MACLKSSM.DOC





				  MACREL/LINK
			    Software Support Manual

				  AA-J073A-TA
















				  DISCLAIMER

		This document file was created by scanning  the
		original  document and then editing the scanned
		text.  As much as possible, the  original  text
		format  was restored.  Some format changes were
		made to insure this  document  would  print  on
		current laser printers using 60 lines per page.
		The  original  spelling  and  grammar  has been
		preserved.


		1-Apr-1997




						     MACREL/LINK
						Software Support Manual

						     AA-J073A-TA













				September 1980

	This manual describes the internal data structures and processes
	of the MACREL Assembler and the LINK Linking Loader. Its purpose
	is to provide experienced users with the detailed technical
	information necessary to allow them to effectively maintain or
	modify these programs.


	This is a new document.

	OPERATING SYSTEM:				OS/8 Version 3D

	SOFTWARE: MACREL				Version 2C
							LINK Version 2AG
















     ----------------------------------------------------------------------
     | To order additional copies of this document, contact the Software  |
     | Distribution  Center,  Digital  Equipment  Corporation,   Maynard, |
     | Massachusetts 01754						  |
     ----------------------------------------------------------------------

	    digital equipment corporation - maynard, massachusetts








					     First Printing, September 1980


     The information in this document is subject to change  without  notice
     and  should  not  be  construed  as  a commitment by Digital Equipment
     Corporation.  Digital Equipment Corporation assumes no  responsibility
     for any errors that may appear in this document.

     The software described in this document is furnished under  a  license
     and  may  only  be used or copied in accordance with the terms of such
     license.

     No responsibility is assumed for the use or reliability of software on
     equipment that is not supplied by DIGITAL or its affiliated companies.






	     Copyright (c) 1980, by Digital Equipment Corporation.
			      All Rights Reserved.





     The postage-prepaid READER'S COMMENTS form on the last  page  of  this
     document  requests  the  user's  critical  evaluation  to assist us in
     preparing future documentation.

     The following are trademarks of Digital Equipment Corporation:

	  DEC		      DECnet		  IAS
	  DECUS		      DECsystem-10	  MASSBUS
	  Digital Logo	      DECSYSTEM-20	  PDT
	  PDP		      DECwriter		  RSTS
	  UNIBUS	      DIBOL		  RSX
	  VAX		      EduSystem		  VMS
						  VT










				    M10000





				   CONTENTS

								       Page

     PREFACE								xi

     PART     I	       MACREL

     CHAPTER  1	       INTRODUCTION				       1-1

	      1.1      SYSTEM LAYOUT				       1-1
	      1.1.1      Resident Code				       1-1
	      1.1.2	 Overlay Code				       1-2
	      1.2      IMPLEMENTATION LANGUAGE			       1-2
	      1.3      LABEL AND SYMBOL CONVENTIONS		       1-2
	      1.3.1	 Directive Routine Labels		       1-3
	      1.3.2	 Labels for Macro-Processing Modules	       1-3
	      1.3.3	 Global Symbol Definition File (MGLOB.MA)      1-3
	      1.3.4	 Labels for Commonly Used Routines and
			 Constants				       1-3
	      1.3.5      Local (Page) Symbols			       1-6
	      1.4      ROUTINE CALLING CONVENTIONS		       1-6
	      1.4.1      ERROR Routine Calls			       1-6
	      1.4.2	 Subprogram Interfaces and Calling Sequences   1-6
	      1.4.3	 Overlay Module Calling Conventions	       1-7
	      1.5      DATA FORMATS AND REPRESENTATIONS		       1-7
	      1.5.1	 Character Encoding and Packing Schemes	       1-8
	      1.5.2	 15-Bit Pointers			       1-8
	      1.5.3	 Chunks					       1-9
	      1.5.4	 Symbol Table Organization		       1-9
	      1.5.4.1    Character Codes for Symbol Table Entries      1-9
	      1.5.5	 Symbol Table Entry Formats		       1-9
	      1.5.5.1	 Regular Symbol Table Entry Format	       1-10
	      1.5.5.2	 .MACRO Symbol Table Entry Format	       1-12
	      1.5.5.3	 Pseudo-Operator and Pseudo-Macro Symbol
			 Table Entry Format			       1-12
	      1.5.5.4	 .EXTERNAL Symbol Table Entry Format	       1-13
	      1.5.5.5	 .ASECT Symbol Table Entry Format	       1-13
	      1.5.5.6	 .DSECT Symbol Table Entry Format	       1-14
	      1.5.5.7	 .RSECT Symbol Table Entry Format	       1-14
	      1.5.5.8	 .FSECT .XSECT and .ZSECT Symbol Table
			 Entry Format				       1-15
	      1.5.5.9	 Auxiliary Symbol Table Chunk Entry Format     1-15
	      1.6      TABLES, STACKS, AND BUFFERS		       1-16
	      1.7      DEFAULT CONDITIONS			       1-17
	      1.8      ERROR AND EXCEPTION REPORTING		       1-18

     CHAPTER  2	       DESCRIPTIONS OF THE MODULES		       2-1

	      2.1      EXPOVR (Overlay 32)			       2-2
	      2.1.1	 BACKL					       2-2
	      2.1.2	 IDIV					       2-4

				      iii



				   CONTENTS

								       Page

	      2.1.3	 IMUL					       2-4
	      2.1.4	 SNGLQQ					       2-5
	      2.1.5	 UPAROQ					       2-5
	      2.2      FIN0 (Overlay 10)			       2-7
	      2.2.1	 NEXTT					       2-7
	      2.2.2	 OPEN1					       2-8
	      2.2.3	 OPEN2					       2-8
	      2.2.4	 OPEN3					       2-8
	      2.2.5	 OPEN4					       2-10
	      2.2.6	 FIN5					       2-10
	      2.2.7	 AINIT					       2-11
	      2.2.8	 CPYTOC					       2-12
	      2.2.9	 REIT					       2-13
	      2.2.10	 IOINIT					       2-13
	      2.2.11	 IONIT2					       2-14
	      2.3      FIN2 (Overlays 12 and 14)		       2-14
	      2.3.1	 Unlabeled Routine			       2-14
	      2.3.2	 LSDOUT (Overlay 12)			       2-16
	      2.3.3	 ZPAD (Overlay 12)			       2-18
	      2.3.4	 LSDINI (Overlay 14)			       2-18
	      2.3.5	 FINIO (Macio)				       2-19
	      2 4      FIN3 (Overlays 11 and 13)		       2-20
	      2 4.1	 Unlabeled Routine (Overlay 11)		       2-20
	      2.4.2	 STPRNT (Overlay 11)			       2-22
	      2.4.3	 PRNT2 (Overlay 11)			       2-23
	      2.4.4	 PRN (Overlay 13)			       2-23
	      2.4.5	 XPRINT (Overlay 13)			       2-23
	      2.4.6	 PRNT6 (Overlay 13)			       2-25
	      2.5      MACERR (Special Overlay)			       2-25
	      2.5.1	 Error Typeout Routines			       2-26
	      2.5.2	 Creating New Error Messages		       2-27
	      2.5.3	 Number of Errors Detected		       2-29
	      2.6      MACEXP					       2-29
	      2.6.1	 EXPR					       2-29
	      2.6.2	 TERM					       2-31
	      2.7      MACINI					       2-33
	      2.7.1	 DATE					       2-33
	      2.7.2	 ONCE					       2-34
	      2.7.3	 CORE					       2-34
	      2.7.4	 LIMSET					       2-34
	      2.7.5	 PREFORM				       2-35
	      2.7.6	 SYMINI					       2-35
	      2.8      MACIO					       2-36
	      2.8.1	 IOINIT and IONIT2			       2-37
	      2.8.2	 FINIO (MACIO)				       2-37
	      2.8.3	 READOS					       2-37
	      2 8 4	 SWITCH					       2-38
	      2 8 5	 SWBACK					       2-39
	      2.8.6	 GETOS and ORET Coroutines		       2-39
	      2.8.7	 MGET and RGET Coroutines		       2-40

				      iv



				   CONTENTS

								       Page

	      2.8.8	 ZGET					       2-40
	      2.8.9	 OFIX					       2-40
	      2.8.10	 SPUSH					       2-40
	      2.8.11	 SPOP					       2-41
	      2.8.12	 LOCPSH					       2-42
	      2.8.13	 LOCPOP					       2-42
	      2.8.14	 OFETCH					       2-42
	      2.8.15	 PUTBUF					       2-42
	      2.8.16	 LISTOR, LSTRET, and OUTLST		       2-42
	      2.8.17	 CONV					       2-42
	      2.8.18	 DELETE					       2-42
	      2.8.19	 LOOKU					       2-43
	      2.8.20	 ZINIT					       2-43
	      2.9      MACLIT (Overlay 31)			       2-43
	      2.9.1	 ZSECTG					       2-43
	      2.9.2	 ZL					       2-44
	      2.9.3	 GENUN					       2-44
	      2.9.4	 ZLIT					       2-44
	      2.9.5	 PRGSPL					       2-45
	      2.9.6	 KLU10					       2-45
	      2.9.7	 PURGEL					       2-45
	      2.9.8	 OUTLIT					       2-45
	      2.9.9	 CMNMOV					       2-46
	      2.10     MACMAC (Overlays 26, 27, and 30)		       2-47
	      2.10.1	 $MACRO					       2-47
	      2.10.2	 PART2					       2-47
	      2.10.3	 $REPT					       2-47
	      2.10.4	 MC					       2-48
	      2.10.5	 $MEXIT					       2-48
	      2.11     MACOPN (Overlay 33)			       2-48
	      2.11.1	 OPEN					       2-48
	      2.11.2	 OPENTC					       2-49
	      2.11.3	 OFETCH					       2-49
	      2.12     MACORG (Overlay 7)			       2-49
	      2.13     MACRO					       2-49
	      2.14     MACRTH (Overlay 6)			       2-51
	      2.15     MACTBL					       2-52
	      2.16     MAC2					       2-52
	      2.16.1	 PUXBIN					       2-53
	      2.16.2	 BPUT					       2-53
	      2.16.3	 PUNBIT					       2-53
	      2.16.4	 PUTBIT					       2-54
	      2.16.5	 ORIG					       2-54
	      2.16.6	 PUTB					       2-54
	      2.16.7	 PUNY					       2-54
	      2.16.8	 PUTLC					       2-54
	      2.16.9	 UNNAM					       2-54
	      2.17     MAC24					       2-55
	      2.17.1	 NEX					       2-55
	      2.17.2	 GETLSD					       2-55

				       v



				   CONTENTS

								       Page

	      2.17.3	 IGNORE					       2-55
	      2.17.4	 CNVADR					       2-55
	      2.17.5	 $PAUSE					       2-55
	      2.17.6	 HGHSCT					       2-56
	      2.17.7	 LOAD					       2-57
	      2.17.8	 SETIT					       2-57
	      2.17.9	 PRZLIT					       2-57
	      2.17.10	 PRGLIT					       2-57
	      2.17.11	 BACKSL					       2-57
	      2.17.12	 ERROR					       2-57
	      2.17.13	 NEXTCHAR				       2-58
	      2.17.14	 GETSYM					       2-58
	      2.17.15	 PUTSYM					       2-58
	      2.17.16	 READLN					       2-59
	      2.17.17	 $FIXMRI				       2-59
	      2.17.18	 EQL					       2-60
	      2.17.19	 GETCHR					       2-60
	      2.17.20	 SCAN					       2-60
	      2.17.21	 GET					       2-60
	      2.17.22	 CTRLC					       2-60
	      2.17.23	 FINI					       2-60
	      2.17.24	 BACKUP					       2-60
	      2.17.25	 BRAN					       2-61
	      2.17.26	 NUMLCL					       2-61
	      2.17.27	 BRANCH					       2-61
	      2.17.28	 ASEMBL					       2-62
	      2.17.29	 GETEX					       2-62
	      2.17.30	 ASEMLV					       2-62
	      2.17.31	 OUTDATA				       2-62
	      2.17.32	 TAGCOM					       2-62
	      2.17.33	 TAGCOL					       2-62
	      2.17.34	 ORIGIN					       2-62
	      2.17.35	 LETTER					       2-63
	      2.17.36	 TSTMAC					       2-63
	      2.17.37	 DIGIT					       2-63
	      2.17.38	 ROTL6					       2-63
	      2.17.39	 PARSYM					       2-63
	      2.17.40	 EOS					       2-64
	      2.17.41	 LOOP					       2-64
	      2.17.42	 CALLIT					       2-64
	      2.17.43	 GETKAR					       2-65
	      2.17.44	 PUSH					       2-65
	      2.17.45	 POP					       2-65
	      2.17.46	 LOOKUP					       2-65
	      2.17.47	 CREF					       2-65
	      2.17.48	 ENTER					       2-66
	      2.17.49	 KLU4					       2-66
	      2.18     MAC30 (Overlay 15)			       2-66
	      2.18.1	 PRINTY					       2-66
	      2.18.2	 PRLINO (MAC2)				       2-66

				      vi



				   CONTENTS

								       Page

	      2.18.3	 SETT					       2-67
	      2.18.4	 DPRINT					       2-67
	      2.18.5	 OPRINT					       2-67
	      2.18.6	 NPRINT					       2-67
	      2.18.7	 CRLF					       2-67
	      2.18.8	 LIST					       2-68
	      2.18.9	 PRNDSH					       2-68
	      2.18.10	 PRNBIN					       2-68
	      2.18.11	 TAB					       2-68
	      2.19     MAC3R					       2-68
	      2.19.1	 OUT					       2-68
	      2.19.2	 NEWPAG					       2-69
	      2.19.3	 LISTER					       2-70
	      2.19.4	 OVRLIN					       2-70
	      2.19.5	 PASS3					       2-70
	      2.20     OVRA (Overlay 1)				       2-70
	      2.20.1	 $PAGE					       2-71
	      2.20.2	 $ZBLOCK				       2-71
	      2.20.3	 $TEXT					       2-71
	      2.21     OVRB (Overlay 2)				       2-72
	      2.21.1	 $IFNZRO				       2-72
	      2.21.2	 $IFZERO				       2-73
	      2.21.3	 $IFDEF					       2-73
	      2.21.4	 $IFNDEF				       2-73
	      2.21.5	 $IF					       2-73
	      2.22     OVRC (Overlay 3)				       2-74
	      2.22.1	 TASKY					       2-74
	      2.22.2	 $OCTAL					       2-75
	      2.22.3	 $DECIMA				       2-75
	      2.22.4	 $RADIX					       2-75
	      2.22.5	 $FILENA				       2-75
	      2.22.6	 $DEVICE				       2-76
	      2.22.7	 $ENABLE				       2-76
	      2.22.8	 $DISABL				       2-78
	      2.23     OVRD (Overlays 4 and 35)			       2-78
	      2.24     OVRE (Overlay 5)				       2-79
	      2.24.1	 $CHAIN					       2-79
	      2.24.2	 $INCLUD				       2-79
	      2.24.3	 $ENTRY					       2-80
	      2.24.4	 $EXTERN				       2-80
	      2.24.5	 $ZTRNA					       2-80
	      2.24.6	 $GLOBAL				       2-80
	      2.24.7	 GLOB2					       2-80
	      2.25     OVRQ (Overlays 21 and 34)		       2-81
	      2.25.1	 BLKLET					       2-81
	      2.25.2	 OUTBLK					       2-81
	      2.25.3	 BINFO					       2-82
	      2.26     OVRR (Overlay 22)			       2-82
	      2.26.1	 $XLIST					       2-82
	      2.26.2	 PREFIN					       2-82

				      vii



				   CONTENTS

								       Page

	      2.26.3	 $NOPUNC				       2-83
	      2.26.4	 $ENPUNC				       2-83
	      2.26.5	 $JSW, $VERSIO, and $START		       2-83
	      2.26.6	 $NOLIST and $LIST			       2-83
	      2.27     OVRS (Overlay 23)			       2-84
	      2.27.1	 $FIXTAB				       2-84
	      2.27.2	 $EXPUNGE				       2-84
	      2.28     OVRT (Overlay 24)			       2-84
	      2.28.1	 LNKCHN					       2-84
	      2.28.2	 KRFCHN					       2-85
	      2.28.3	 $FIELD					       2-85
	      2.29     OVRU (Overlay 25)			       2-85
	      2.29.1	 $SBTTL					       2-85
	      2.29.2	 $EJECT					       2-85
	      2.29.3	 $TITLE					       2-86
	      2.29.4	 $RELOC					       2-86
	      2.29.5	 $PUSH and $POP				       2-86
	      2.30     PAS2 (Overlay 16)			       2-86
	      2.30.1	 PUTBN					       2-87
	      2.30.2	 CHKFUL					       2-87
	      2.30.3	 PUTBT					       2-87
	      2.30.4	 GETFLG					       2-88
	      2.30.5	 BPUTX					       2-88
	      2.30.6	 CREFX					       2-88
	      2.30.7	 MORCRF					       2-88


























				     viii



				   CONTENTS

								       Page


     PART     II       LINK

     Chapter  3	       INTRODUCTION				       3-1

	      3.1      INTRODUCTION				       3-1
	      3.2      SYSTEM LAYOUT				       3-1
	      3.3      IMPLEMENTATION LANGUAGE			       3-1
	      3.4      LABEL AND SYMBOL CONVENTIONS		       3-1
	      3.5      ROUTINE CALLING CONVENTIONS		       3-2
	      3.6      DATA FORMATS AND REPRESENTATIONS		       3-2
	      3.7      TABLES					       3-2
	      3.7.1	 Global Symbol Table (GST)		       3-2
	      3.7.2	 Binary Buffer Table (LDBUFS)		       3-4
	      3.7.3	 Pointer Table (PTRTAB)			       3-5
	      3.7.4	 Module Descriptor Table (MODTAB)	       3-5
	      3.7.5	 .SECT Table (SECTAB)			       3-5
	      3.7.6	 Core Image Table (CIMAG, CIMAGl, CIMAG2,
			 and CIMAGE)				       3-8
	      3.7.7	 Overlay Transfer Vector (TRANVC)	       3-8
	      3.7.8	 User Overlay Level Data Table (QUSRLV)	       3-9
	      3.7.9	 Overlay Level Information Table (LHDR)	       3-10
	      3.7.10	 Main Binary Section Table (MBST)	       3-10
	      3.7.11	 Memory Segment Control Double Words	       3-12
	      3.7.12	 Library Table (LIBTB)			       3-12
	      3.8      DEFAULT CONDITIONS			       3-12
	      3.9      LINK ERROR AND EXCEPTION REPORTING	       3-14

     CHAPTER  4	       DESCRIPTIONS OF THE MODULES		       4-1

	      4.1      LNKALL					       4-1
	      4.2      LNKBN1 AND LNKBN2			       4-3
	      4.3      LNKCAL					       4_4
	      4.4      LNKCD					       4-5
	      4.5      LNKMAN					       4-5
	      4.6      LNKLSD					       4-8
	      4.7      LNKMSG					       4-10
	      4.8      LNKMAP					       4-10

     APPENDIX A	       CHARACTER SETS				       A-1

     APPENDIX B	       MACREL MAINTENANCE PROCEDURES		       B-1

     APPENDIX C	       SUMMARY OF MACREL'S MAJOR MODULES	       C-1

     APPENDIX D	       BATCH FILES FOR ASSEMBLING AND LINKING MACREL,
		       LINK, AND KREF				       D-1

     APPENDIX E	       MEMORY UTILIZATION AND MODULE SUMMARY	       E-1


				      ix



				   CONTENTS

								       Page

     APPENDIX F	       MACREL COMMAND DECODER OPTIONS		       F-1

     APPENDIX G	       DISCUSSION OF SELECTED ROUTINES IN LINK	       G-1

	      G.1      ADJPTR (LNKLSD)				       G-1
	      G.2      ALLOC (LNKALL)				       G-1
	      G.3      BULDTV (LNKBN2)				       G-1
	      G.4      CPIC (LNKALL)				       G-2
	      G.5      NEWBB (LNKBN2)				       G-2
	      G.6      NEWORG (LNKBN2)				       G-2
	      G.7      PUTBIN (LNKBN2)				       G-2
	      G.8      RELOCA (LNKBN2)				       G-2
	      G.9      SEARCH (LNKMAN)				       G-3
	      G.10     SSORT (LNKALL, LNKLSD, and LNKMAP)	       G-3

     INDEX							   Index-1




				    FIGURES

     FIGURE   1-1      OS/8 ASCII Character Packing		       1-8
	      1-2      15-Bit Pointer Format			       1-9
	      2-1      Memory Limit Table (LIMTBL) Layout	       2-35
	      2-2      Formal Argument Table Entry Format	       2-47
	      2-3      Actual (macro) Argument Table Layout	       2-51
	      3-1      Main Binary Section Table Layout		       3-11
	      3-2      Library Table Layout			       3-13
	      D-1      BATCH File for Building MACREL, LINK, and
		       KREF					       D-2




					   TABLES

     TABLE    1-1      Summary of Commonly Used Resident (Field 0)
		       Routines					       1-4
	      1-2      Symbol Table Flag Word			       1-10
	      1-3      Format for Regular Symbol Table Entries	       1-11
	      1-4      Format for Regular Symbol Table Entries with
		       Extended Names				       1-11
	      1-5      Extended Symbol Name Field Definitions	       1-12
	      1-6      Format for .MACRO Symbol Table Entries	       1-12
	      1-7      Format for Pseudo-Operators (PSEUD) and
		       Pseudo-Macros (PSEUM) Symbol Table Entries      1-13
	      1-8      Format for .EXTERNAL Symbol Table Entries       1-13
	      1-9      Format for .ASECT Symbol Table Entries	       1-14
	      1-10     Format for .DSECT Symbol Table Entries	       1-14

				       x



				   CONTENTS

								       Page

	      1-11     Format for .RSECT Symbol Table Entries	       1-15
	      1-12     Format for .XSECT, .ZSECT, and .FSECT
		       Symbol Table Entries			       1-15
	      1-13     Symbol Table Layout for Auxiliary Chunks
		       (.SECTs only)				       1-16
	      1-14     Summary of Tables, Stacks, and Buffers	       1-17
	      2-1      MACREL Module Summary			       2-1
	      2-2      Basic Letter Block Widths vs Listing Device
		       Column Width				       2-9
	      2-3      LSD Entry Type Codes			       2-17
	      2-4      Loader Symbol Dictionary Entry Types,
		       Destinations, and Tasks			       2-24
	      2-5      Layout of MACERR Within MACREL.SV	       2-26
	      2-6      MACERR Output Routine Summary		       2-26
	      2-7      Local Variables Saved on the Expression Stack   2-30
	      2-8      EXPR Previous Operator Dispatch Table	       2-31
	      2-9      TERM Character Dispatch Table		       2-31
	      2-10     Internal Storage Format of OS/8 Date Words      2-33
	      2-11     Initial Symbol Table Entry Format	       2-36
	      2-12     Symbol Table Flags Definitions		       2-40
	      2-13     Summary of Routines in the MACRO Module	       2-50
	      2-14     Descriptions of MACRTH Routines		       2-51
	      2-15     Character Branch Table (MACTBL) Classification
		       Codes					       2-53
	      2-16     Assembly Listing Symbol Name Qualifiers	       2-66
	      2-17     TEXT Directive Coroutines		       2-72
	      2-18     .IF Directive Conditions			       2-74
	      2-19     $ENABLE Condition Options		       2-76
	      2-20     $DISABL Condition Options		       2-78
	      2-21     OVRD Entry Points and CST Values		       2-78
	      3-1      Global Symbol Table Entry Format		       3-3
	      3-2      Global Symbol Table Symbol Type Codes	       3-4
	      3-3      Number of Binary Buffers as a Function of
		       Memory Size				       3-5
	      3-4      Module Descriptor Table Format		       3-6
	      3-5      .SECT Table Format			       3-6
	      3-6      Core Image Table Format			       3-8
	      3-7      Overlay Transfer Vector Format		       3-9
	      3-8      Overlay Level Data Table Format		       3-10
	      3-9      Overlay Information Table Entry Format	       3-10
	      3-10     Memory Segment Control Double Word Entry
		       Format					       3-12
	      4-1      Routines in LNKMAN			       4-6
	      A-1      MACREL Special 6-bit Character Codes	       A-1
	      A-2      ASCII Character Set			       A-1
	      E-1      MACREL Memory Utilization		       E-1
	      E-2      Overlay Module Data Summary		       E-4




				      xi






				    PREFACE


     ABOUT THIS MANUAL

     The MACREL/LINK Software Support Manual describes  the  internal  data
     _______________________________________
     structures  and processes of the MACREL Assembler and the LINK Linking
     Loader.  Its purpose is to provide experienced users with the detailed
     technical  information necessary to allow them to effectively maintain
     or modify these programs.

     To use this manual effectively, you must be completely  familiar  with
     PDP/8  computer  hardware  and  macro  assembler programming using the
     MACREL and LINK programs.   You should  also  be  familiar  with  OS/8
     system operation and OS/8 terminology.

     The manual is designed for use in  conjunction  with  the  MACREL/LINK
								___________
     User's  Manual  and the MACREL and LINK assembly listings.  Though the
     ______________
     listings are well commented, but some of the comments may be obsolete.
     If  there  is a conflict between the listing comments and this manual,
     this manual takes precedence.

     The manual is divided into two parts: Part 1, MACREL; Part 2, LINK.



     SYNOPSIS

     Chapter 1 introduces the MACREL assembler and describes  its  internal
     structure and conventions.

     Chapter 2 consists of detailed descriptions of the major  routines  in
     each  of MACREL's source modules.  The chapter presents the modules in
     alphabetical order by module name.

     Chapter 3  introduces  the  LINK  linking  loader  and  describes  its
     internal structure and conventions.

     Chapter  4  consists  of  functional  descriptions  of  LINK's  source
     modules.   The  chapter  presents the modules in alphabetical order by
     module name.

     The appendixes contain MACREL  and  LINK  batch  assembly  procedures,
     MACREL   maintenance  procedures,  summary  descriptions  of  MACREL's
     overlays and major routines, character codes.







				      xii



     REFERENCES TO DOCUMENTS

     The  text  of  this  manual  contains  references  to  the   following
     documents:

	  MACREL/LINK User's Manual (AA-5664A-TA)
	  _________________________

	  OS/8 Language Reference Manual (PAL8 section) (AA-H609A-TA)
	  ______________________________

	  MACREL and LINK Assembly Listings (contained in files residing on
	  _________________________________
	  DECtapes:     AL-5643B-SA    (MACREL);    AL-5644B-SA   (MACREL);
	  AL-H602B-SA (LINK);  AL-H603B-SA (LINK)



     DOCUMENT CONVENTIONS

     This section describes the  conventions  and  symbology  used  in  the
     manual.

	  o  Fully capitalized words in the text are the  names  of  either
	     source modules, routines, entry points, or variables.

	  o  References to  routines,  entry  points,  and  variables  that
	     reside  in  a  module  other  than the one being discussed are
	     followed by the module  name  enclosed  in  parentheses.   For
	     example,  in the discussion of the PAS2 module, a reference to
	     the QPUT routine in module MACIO would appear as:

	     ...  text ...  QPUT (MACIO) ...  text ...

























				     xiii





























				    PART I

				    MACREL






				   CHAPTER 1

				 INTRODUCTION


     MACREL is a four-pass assembler.  Pass 1 defines all the  symbols  and
     creates the table-of-contents.  Pass 2 creates the binary output file.
     Pass 3 creates the listing file.  Pass 4 creates the data file used by
     the KREF program to generate a cross-reference listing.  Four separate
     passes are necessary because the OS/8 operating system does not permit
     more than one output file to be open on the same device.

     MACREL accepts input from various sources called input streams,  which
     may  be internal or external.  The main input stream is the OS/8 input
     file that contains the user's  source  program.   MACREL  switches  to
     other input streams in response to the following directives and macros
     in the source file:

	  o  The .CHAIN directive permanently switches the input stream  to
	     another, external, OS/8 input file.

	  o  The .INCLUDE directive temporarily switches the  input  stream
	     to another, external, OS/8 input file.

	  o  A macro invocation switches the input stream  to  an  internal
	     source called the macro input stream.

	  o  The real arguments to a macro switch the input  stream  to  an
	     internal source called the argument input stream.

	  o  The .REPT directive switches the input stream to  an  internal
	     source called the repeat input stream.

     The streams are controlled by a switching control  routine  and  input
     coroutines.   The  switching  control routine uses a software pushdown
     stack to preserve the entire state of a coroutine so that input can be
     switched from one routine to another and back without loss of context.
     The input coroutines fetch characters from their associated sources.



     1.1  SYSTEM LAYOUT

     The following  paragraphs  describe  the  memory  layout  of  MACREL's
     resident  and  overlay  code.  Table E-1 (Appendix E) shows the memory
     allocation for each MACREL module.



     1.1.1  Resident Code


				      1-1
				 INTRODUCTION


     MACREL's resident code consists of seven modules:  MAC2, MAC24, MAC3R,
     MACEXP, MACIO, MACRO and MACTBL.  MAC24 is the main module and resides
     in Field 0.  It contains the assembler's main processing  loop,  which
     issues calls to all other modules.



     1.1.2  Overlay Code

     MACREL's overlay code consists of 28 modules (see Appendix E).  During
     execution these modules reside in one of four primary overlay areas:

	  1.  Directives Overlay Area.  Contains the overlays that  process
	      MACREL's directives.

	  2.  Pass Specific Overlay Area.  Contains the overlays  that  are
	      functionally related to the current assembly pass.

	  3.  Auxiliary Overlay Area.  Contains extension overlays  to  the
	      overlays  that  cannot  reside completely in one of the other
	      overlay areas.


				     NOTE

			When this area is not  used  to  contain
			overlay           extensions          to
			directive-processing    routines,     it
			contains   the   overlays  that  process
			little-used  expression  constructs  and
			complex  relocatable expressions.  It is
			important   to   note   therefore   that
			overlays   that   call   the  expression
			processor (MACEXP) must  not  load  code
			into this area.


	  4.  Extremities Overlay Area.   Contains  overlays  that  perform
	      end-of-pass  processing  (FIN  code)  and  start-of-next-pass
	      initialization code.  During specific passes,  this  area  is
	      the input buffer (INPBUF).



     1.2  IMPLEMENTATION LANGUAGE

     MACREL is coded in itself.  Since it is written to run  on  all  PDP-8
     processors, it does not use the MQ register.



     1.3  LABEL AND SYMBOL CONVENTIONS



				      1-2
				 INTRODUCTION


     1.3.1  Directive Routine Labels

     Labels for entry points to routines  that  implement  MACREL  language
     directives  begin  with  a dollar sign ($) followed by the name of the
     directive.   For  example,  the  routine  that  implements  the   PAGE
     directive is labeled $PAGE.

     A period (.) is not included in the label for a directive that  has  a
     leading period in its name.  For example, the code that implements the
     .CHAIN directive is labeled $CHAIN.  Only  the  first  (leftmost)  six
     characters  of  a  MACREL symbol, excluding a leading dollar sign ($),
     are significant.   Thus,  the  labels  for  the  directive  processing
     routines  may  not exactly match their directive keyword counterparts.
     For example, the routine that  implements  the  DECIMAL  directive  is
     labeled $DECIMA.



     1.3.2  Labels for Macro-Processing Modules

     Many of  the  modules  related  to  processing  of  macros  and  their
     arguments  have  labels consisting of one or two letters and a number.
     These numbers correspond to the step numbers given in comments at  the
     beginning of the module.



     1.3.3  Global Symbol Definition File (MGLOB.MA)

     The global symbol definition file is a parameter file that consists of
     global  symbol  definitions.   The  symbols  are referenced by a large
     number of MACREL's source  modules.   The  beginning  of  each  source
     module  contains  an .INCLUDE MGLOB.MA directive to make sure that the
     assembler reads the symbol definitions  before  assembling  a  module.
     The  file  establishes the common symbolic linkages between the source
     modules.  When assembling a module, you must be sure  that  this  file
     resides on the OS/8 device assigned to DSK:.


				    CAUTION

		    Do not change  the  value  of  a  global
		    symbol  by  redefining  it in one of the
		    modules.  You must make  the  change  in
		    MGLOB.MA  and  then  reassemble  all the
		    MACREL source modules  to  complete  the
		    process.



     1.3.4  Labels for Commonly Used Routines and Constants

     Labels to commonly used routines prefixed with the letters QQ are part
     of  the  Field 0 resident code and are transfer vectors.  For example,

				      1-3
				 INTRODUCTION


     JMS I QQENTER is a subroutine call to the ENTER routine  that  resides
     in Field 0 in the MAC24 module.  Table 1-1 contains a summary of these
     routines.  Commonly used constants  may  use  either  a  QQ  (positive
     constant)  or  QM  (minus constant) prefix.  For example, QQ177 is the
     constant 177, while QM10 is the constant -10 (7770).


				   Table 1-1
	     Summary of Commonly Used Resident (Field 0) Routines

     ----------------------------------------------------------------------
     | Name		|		Function			  |
     |------------------|-------------------------------------------------|
     | ASEMLV		| Sends the currently assembled statement to  the |
     |			| binary file.					  |
     |			|						  |
     | BACKUP		| Moves the line buffer pointer (LINPTR) back one |
     |			| position.					  |
     |			|						  |
     | BRAN		| Performs an indexed  branch  into  a  table  of |
     |			| addresses, and branches to the selected address.|
     |			|						  |
     | CREF		| Sends  the  symbol   name   and   line   number |
     |			| information to the cross reference (KREF) file. |
     |			|						  |
     | CRLF		| Sends a carriage return /line feed sequence  to |
     |			| the listing file.				  |
     |			|						  |
     | DPRINT		| Sends the decimal  number  in  the  accumulator |
     |			| (AC) to the number-printing routine NPRINT.	  |
     |			|						  |
     | ENTER		| Enters a symbol in the symbol table  when  that |
     |			| symbol  is  specified  in the symbol table work |
     |			| area.						  |
     |			|						  |
     | EOS		| Determines whether  the  current  character  in |
     |			| BITS is a statement delimiter.		  |
     |			|						  |
     | ERROR		| Calls the error message processor to  print  an |
     |			| error message.				  |
     |			|						  |
     | EXPR		| Parses a term and returns the absolute part  of |
     |			| the  result  in  the  accumulator  (AC) and the |
     |			| relative part in EXPREL.			  |
     |			|						  |
     | GETCHR		| Obtains a character from the  line  buffer  and |
     |			| determines its type code.			  |
     |			|						  |
     | GETKAR		| Obtains a character from the line buffer.	  |
     |			|						  |
     | GETSYM		| Loads a copy of a symbol table entry  into  the |
     |			| symbol table work area.			  |
     ----------------------------------------------------------------------
						(continued on next page)

				      1-4
				 INTRODUCTION


			      Table 1-1  (Cont.)
	     Summary of Commonly Used Resident (Field 0) Routines

     ----------------------------------------------------------------------
     | Name		|		Function			  |
     |------------------|-------------------------------------------------|
     | HGHSCT		| Obtains the highest address used by  a  program |
     |			| section.					  |
     |			|						  |
     | LETTER		| Determines if the current character  (CHAR)  is |
     |			| an  upper-case  or  lower-case letter, a period |
     |			| (.) or a dollar sign ($).			  |
     |			|						  |
     | LISTER		| Sends characters to the listing file.		  |
     |			|						  |
     | LOOKUP		| Searches the symbol table for a symbol.	  |
     |			|						  |
     | OPRINT		| Sends the octal number in the accumulator  (AC) |
     |			| to the number-printing routine NPRINT.	  |
     |			|						  |
     | ORIG		| Sets up the flag word (FLG)  and  sends  a  new |
     |			| location counter (PC) value to the binary file. |
     |			|						  |
     | OUT		| Sends a line to the listing file.		  |
     |			|						  |
     | PARSYM		| Parses a symbol from the current input stream.  |
     |			|						  |
     | PASS3		| Determines if a pass is pass 3.		  |
     |			|						  |
     | POP		| Removes (pops)  a  value  from  the  expression |
     |			| stack and leaves it in the accumulator (AC).	  |
     |			|						  |
     | PUNBIT		| Sends a binary entry and its flag field to  the |
     |			| binary  file;   prints  the current line during |
     |			| Pass 3.					  |
     |			|						  |
     | PUSH		| Places (pushes) the contents of the accumulator |
     |			| (AC) on the expression stack.			  |
     |			|						  |
     | PUTBIT		| Sends a binary entry without a  flag  field  to |
     |			| the binary file during pass 2.		  |
     |			|						  |
     | PUTSYM		| Inserts the data in the symbol table work  area |
     |			| into to the symbol table.			  |
     |			|						  |
     | PUXBIN		| Sends a binary entry and its flag field to  the |
     |			| binary file.					  |
     |			|						  |
     | READLN		| Reads a logical line of text from  the  current |
     |			| input stream into the line buffer.		  |
     ----------------------------------------------------------------------
						(continued on next page)



				      1-5
				 INTRODUCTION


			      Table 1-1  (Cont.)
	     Summary of Commonly Used Resident (Field 0) Routines

     ----------------------------------------------------------------------
     | Name		|		Function			  |
     |------------------|-------------------------------------------------|
     | ROTL6		| Rotates the accumulator (AC)  and  the  link  6 |
     |			| bits leftward.				  |
     |			|						  |
     | SCAN		| Skips over a sequence of spaces and tabs.	  |
     ----------------------------------------------------------------------



     1.3.5  Local (Page) Symbols

     In some modules, you will find that unimportant  symbols  are  created
     by  appending  a  single  letter  (or  digit) to the end of the module
     name.  Such symbols are referenced  only  within  the  (listing)  page
     where  they  reside;   they  can  be  converted  to  local  symbols if
     necessary.



     1.4  ROUTINE CALLING CONVENTIONS



     1.4.1  ERROR Routine Calls

     Almost all calls to the ERROR routine have labels of the form:

	  ERnn or IOnn

     where:

	  nn is the error number

     These labels are defined as external symbols in the MACERR module.



     1.4.2  Subprogram Interfaces and Calling Sequences

     Most of MACREL's main routines  reside  in  Field  0,  while  the  I/O
     routines    reside   in   Field   1.    This   minimizes   cross-field
     communication.  When a cross-field call or jump is  necessary,  MACREL
     does  not  use  the  general  PDP-8  calling convention of setting the
     data field to the current field.   This  is  because  MACREL  routines
     know the fields where their callers are located.

     Also, for further efficiency, most Field 0  routines  are  written  so
     that  they  can only be called from Field 0.  For the rare cases where
     it is necessary to call these routines from  Field  1,  the  auxiliary

				      1-6
				 INTRODUCTION


     subroutine  CALLIT  is  used.  For example, if a routine in Field 1 is
     to call a routine SUB in Field 0, the call would be as follows:

	  CIF 0
	  JMS I (CALLIT
	  SUB

     This allows routines to  pass  an  argument  back  and  forth  in  the
     accumulator (AC).



     1.4.3  Overlay Module Calling Conventions

     When control passes to a routine  that  resides  in  an  overlay,  the
     routine  that  is  currently running must call the overlay loader LOAD
     by using the calling sequence described in Section 2.17.7.

     In many cases, the  calling  routine  will  then  pass  control  to  a
     routine  in  the  overlay  by a JMP or JMS to an entry point that is a
     global symbol.  Since the   symbol  will  be  in  the  cross-reference
     listing,  you  can easily locate its origin and other references.  For
     example, if in Overlay 6 there is an entry  point  named  CMPLXE,  the
     call to this code from MAC24 is:

	  JMS I (LOAD
	  AUXOVR+6
	  JMP I (CMPLXE

     The loader loads Overlay 6 into the area  that  begins  with  location
     AUXOVR, and the calling routine then passes control to CMPLXE.

     In other cases, the calling routine will simply pass  control  to  the
     first  location  in  the  overlay  area  rather  than to a named entry
     point of a routine in the overlay.  For  example,  if  in  Overlay  10
     (FIN0),  the  module's  code  begins  with  the tag NEXTT, the call to
     this code from MAC24 is:

	  JMS I (LOAD
	  INHAND+10
	  JMP I .+1
	  INHAND

     The loader loads Overlay 10 into  the  overlay  area  that  begins  at
     INHAND,  and  the  calling  routine  then branches to the beginning of
     the overlay area.  Thus, the call to the entry point  in  the  overlay
     is   difficult  to  locate  in  a  listing,  since  the  call  is  not
     associated with a symbol in the cross-reference listing.



     1.5  DATA FORMATS AND REPRESENTATIONS



				      1-7
				 INTRODUCTION


     This section describes  MACREL's  character  codes,  packing  schemes,
     and data formats, including the symbol table.



     1.5.1  Character Encoding and Packing Schemes

     MACREL  uses  three  different  character  codes  and  two   character
     packing  schemes  for  its  internal operations.  (This is in addition
     to the .ENABLE directive's character packing options described in  the
     MACREL/LINK   User's  Manual.)  The  character  codes  are:   MACREL's
     ____________________________
     special 6-bit code and the ASCII 6-bit and 7-bit codes  (described  in
     Appendix X).  The packing schemes are:  OS/8 and 6-bit.

     MACREL accepts characters for input in 7-bit  ASCII  (the  eighth  bit
     is  ignored),  that  are packed using the OS/8 packing scheme shown in
     Figure 1-1.


		bit 0		    3 4			 11
	           -----------------------------------------
	   word 1  |   character 3   |     character 1     |
	           |   (bits 0 - 3)  |		           |
	           |-----------------|---------------------|
	   word 2  |   character 3   |     character 2     |
	           |   (bits 4 - 7)  |		           |
	           -----------------------------------------
						   ML-027-80

		   Figure 1-1  OS/8 ASCII Character Packing


     For storage in the symbol  table,  MACREL  converts  these  characters
     either  into  MACREL 6-bit code or into 6-bit ASCII code (depending on
     the operation).  It packs  the  characters  two  characters  per  word
     (6-bit  packing)  and  maps the lower-case ASCII characters into their
     upper-case equivalents.

     MACREL converts characters for output into  OS/8  packed  8-bit  ASCII
     (7-bit ASCII with parity bit always set).



     1.5.2  15-Bit Pointers

     The 15-bit pointer is a method for encoding  a  15-bit  address  in  a
     12-bit word.  Figure 1-2 illustrates the format.








				      1-8
				 INTRODUCTION


		bit 0	       2 3	      11
	           ------------------------------
		   |	field	|    address    |
	           ------------------------------
		       ^	    ^
		       |	    |
		       |	    |
		       |	    --- 12-bit location divided by 8. Append
		       |		three zeros to the right of this
		       |		value to obtain the complete
		       |		address.
		       |
		       --- Memory field of location.		  ML-028-80

		       Figure 1-2  15-Bit Pointer Format



     1.5.3  Chunks

     MACREL formats all memory not used by itself or by  OS/8  into  8-word
     groups  called  chunks.   It  links these chunks together into a chain
     from which it  allocates  memory  for  both  symbol  table  and  macro
     storage.   The  first  word  of each chunk contains the 15-bit pointer
     to the next chunk.  Location FREESPACE  contains  the  15-bit  pointer
     to  the  first  chunk  in  the  chain.   The  last  chunk in the chain
     contains a pointer of zeros.



     1.5.4  Symbol Table Organization

     The symbol table is a  collection  of  linked  lists  called  buckets.
     There  are  100  (octal)  buckets  in  the  symbol  table.   They  are
     assigned numbers in the range 0 through 77.  Each bucket  consists  of
     0  or  more  chunks  linked together with 15-bit pointers.  Each chunk
     in a bucket contains the data  for  one  symbol  (that  is,  a  symbol
     table  entry).   Each  entry  is  sorted into one of the buckets.  The
     sort is based on a match between the  bucket  number  and  the  number
     formed  by  the  first  6  bits of the first character of the symbol's
     name (or bits 0 through 5 of word 1 of the symbol table entry).



     1.5.4.1  Character  Codes  for  Symbol  Table  Entries  -  Except  for
     symbol  table  entries  with  extended  names, MACREL uses the special
     character codes shown in Table A-1 (Appendix A)  when  storing  symbol
     names in the symbol table.



     1.5.5  Symbol Table Entry Formats

     MACREL stores a symbol's information in  the  symbol  table  using  an
     entry  format  that  is based on the symbol type.  The flag word (word

				      1-9
				 INTRODUCTION


     5) of each entry specifies the symbol's type as shown  in  Table  1-2.
     The sections that follow describe these formats.


				   Table 1-2
			    Symbol Table Flag Word

     ----------------------------------------------------------------------
     |  Bit	     |	      Meaning					  |
     |		     |	 (when set to 1)				  |
     |---------------|----------------------------------------------------|
     |		     |							  |
     |	0	     |	Symbol is defined				  |
     |	1	     |	Symbol is a memory reference instruction (MRI)	  |
     |	2	     |	Symbol is a permanent symbol			  |
     |	3	     |	Symbol was defined during pass 1		  |
     |	4	     |	Symbol is a local symbol			  |
     |	5	     |	Symbol was defined before being referenced or	  |
     |		     |	is an unnamed program section			  |
     |		     |							  |
     |	6-8	     |	 0 = Not a program section			  |
     |		     |	 1 = .ASECT					  |
     |		     |	 2 = .RSECT					  |
     |		     |	 3 = .FSECT					  |
     |		     |	 4 = .DSECT					  |
     |		     |	 5 = .ZSECT					  |
     |		     |	 6 = .XSECT					  |
     |		     |	 7 = Reserved					  |
     |		     |							  |
     |	9-11	     |	 0 = Regular symbol				  |
     |		     |	 1 = User macro					  |
     |		     |   2 = Pseudo-macro (PSEUM)			  |
     |		     |	 3 = Pseudo-operator (PSEUD) directive		  |
     |		     | * 4 = .ENTRY					  |
     |		     | * 5 = .GLOBAL symbol				  |
     |		     | * 6 = .EXTERNAL					  |
     |		     | * 7 = .ZTERNAL					  |
     ----------------------------------------------------------------------
	* Bit 9 is set to 1 when the symbol belongs to the LSD.
	  If the symbol is undefined, all other bits are ignored.



     1.5.5.1  Regular Symbol Table Entry  Format  -  Table  1-3  shows  the
     format of a symbol table entry for a regular symbol.  If the symbol is
     a numeric local symbol or a literal, it is entered in the symbol table
     as  a regular symbol with an extended name in words 1 through 3 of the
     entry, as shown in Tables 1-4 and 1-5.







				     1-10
				 INTRODUCTION


				   Table 1-3
		    Format for Regular Symbol Table Entries

     ----------------------------------------------------------------------
     |	  Word	  |			Use				  |
     |------------|-------------------------------------------------------|
     |	   0	  | 15-bit pointer to next chunk in the bucket		  |
     |	   1	  | char 0 /char 1					  |
     |	   2	  | char 2 /char 3					  |
     |	   3	  | char 4 /char 5					  |
     |	   4	  | absolute value					  |
     |	   5	  | flag (see Table 1-2)				  |
     |	   6	  | 15-bit .SECT pointer				  |
     |     7	  | LSD number						  |
     ----------------------------------------------------------------------
	Note:   char = character of symbol name in MACREL 6-bit code.


				   Table 1-4
	  Format for Regular Symbol Table Entries with Extended Names

     ----------------------------------------------------------------------
     |  Word |			    Use					  |
     |-------|------------------------------------------------------------|
     |	     |								  |
     |	 0   | 15-bit pointer to next chunk in the bucket		  |
     |	 1   | bits							  |
     |	     |    0-5 = typcode	      = 36 or 76 to signify extended name |
     |	     |    6-11 = prechar      = 6-bit ASCII (space, V or L)	  |
     |	 2   | number		      = symbol name, literal value, or	  |
     |	     |				literal address			  |
     |	 3   | bits							  |
     |	     |    0 = r		      = 0 (octal radix) or 1 (decimal	  |
     |	     |				radix)				  |
     |	     |    1-5 = unused						  |
     |	     |    6-11 = postchar     = 6-bit ASCII ( $ or + )		  |
     |	 4   | absolute value						  |
     |	 5   | flag (see Table 1-2)					  |
     |	 6   | 15-bit .SECT pointer					  |
     |	 7   | LSD number						  |
     ----------------------------------------------------------------------














				     1-11
				 INTRODUCTION


				   Table 1-5
		    Extended Symbol Name Field Definitions

     ----------------------------------------------------------------------
     |	     Use	 | prechar | number  |     r	 |    postchar	  |
     |			 | (6-bit) |	     |  (radix)  |    (6-bit)	  |
     |-------------------|---------|---------|-----------|----------------|
     | Numeric Local	 | <space> | symbol  | name	 | 1 (decimal) $  |
     | Symbol		 |	   |	     |		 |		  |
     |			 |	   |	     |		 |		  |
     | Literal Reference |	   | literal |		 |		  |
     | by Value		 |    V	   | value   | 0 (octal) | + (if	  |
     |			 |	   |	     |		 |   relocatable) |
     | Literal Reference |	   | literal |		 |		  |
     | by Location	 |    L	   | address | 0	 | + (if	  |
     |			 |	   |	     |		 |   relocatable) |
     ----------------------------------------------------------------------



     1.5.5.2  .MACRO Symbol Table Entry Format - Table 1-6 shows the format
     of a symbol table entry for a .MACRO name.


				   Table 1-6
		    Format for .MACRO Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | 15-bit pointer to the first chunk of the macro definition |
     |	 5    | flag (see Table 1-2)					  |
     |	 6    | 15-bit pointer to the last chunk of the macro definition  |
     |	 7    | unused							  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.3   Pseudo-Operator  and   Pseudo-Macro   Symbol   Table   Entry
     Format - Table 1-7 shows the format of a symbol table entry for either
     pseudo-operators or pseudo-macros.








				     1-12
				 INTRODUCTION


				   Table 1-7
	     Format for Pseudo-Operators (PSEUD) and Pseudo-Macros
			 (PSEUM) Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    |	15-bit pointer to next chunk in the bucket		  |
     |	 1    |	char 0 /char 1						  |
     |	 2    |	char 2 /char 3						  |
     |	 3    |	char 4 /char 5						  |
     |	 4    |	12-bit address to Field 0 routine (flag = PSEUD) or entry |
     |	      |	into overlay (PSEUM) if flag = PSEUM.			  |
     |   5    |	flag (see Table 1-2)					  |
     |	 6    |	number of overlay to load if PSEUD, or unused if PSEUM	  |
     |	 7    |	unused							  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.4  .EXTERNAL Symbol Table Entry  Format - Table  1-8  shows  the
     format of a symbol table entry for a .EXTERNAL symbol.


				   Table 1-8
		   Format for .EXTERNAL Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | unused							  |
     |	 5    | flag (see Table 1-2)					  |
     |	 6    | unused							  |
     |   7    | LSD number						  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.5  .ASECT Symbol Table Entry Format - Table 1-9 shows the format
     of a symbol table entry for an .ASECT symbol.







				     1-13
				 INTRODUCTION


				  Table 1-9
		    Format for .ASECT Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | highest current location counter (PC) value in the .ASECT |
     |	 5    | flag (see Table 1-2)					  |
     |	 6    | 15-bit pointer to auxiliary symbol table chunk (See	  |
     |	      | Table 1-13)						  |
     |	 7    | LSD number						  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.6  .DSECT Symbol Table Entry  Format  -  Table  1-10  shows  the
     format of a symbol table entry for a .DSECT symbol.


				  Table 1-10
		    Format for .DSECT Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | lowest current location counter (PC) value in the .DSECT  |
     |	      | (length of the program section)				  |
     |	 5    | flag (See Table 1-2)					  |
     |	 6    | 15-bit pointer to auxiliary symbol table chunk (see	  |
     |	      | Table 1-13)						  |
     |	 7    | LSD number						  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.7  .RSECT Symbol Table Entry  Format  -  Table  1-11  shows  the
     format of a symbol table entry for an .RSECT symbol.






				     1-14
				 INTRODUCTION


				  Table 1-11
		    Format for .RSECT Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | highest relative current location counter (PC) value in	  |
     |	      | the .RESCT (length of the program section)		  |
     |	 5    | flag (see Table 1-2)					  |
     |	 6    | 15-bit pointer to auxiliary symbol table chunk (see	  |
     |	      | Table 1-15)						  |
     |	 7    | LSD number						  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.8  .FSECT .XSECT and .ZSECT Symbol  Table  Entry  Format - Table
     1-12  shows  the  format  of  a  symbol table entry for .FSECT, .XSECT
     and .ZSECT symbols.


				  Table 1-12
		     Format for .XSECT, .ZSECT, and .FSECT
			     Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | highest location counter (PC) value in the program section|
     |	 5    | flag (see Table 1-2)					  |
     |	 6    | 15-bit pointer to auxiliary symbol table chunk (see Table |
     |	      | 1-13)							  |
     |	 7    | LSD number						  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.9  Auxiliary Symbol Table Chunk Entry Format - Table 1-13  shows
     the format of symbol table entry for an auxiliary chunk.  This type of
     entry is used only in conjunction  with  the  program  section  symbol
     table entries described in Sections 1.5.5.5 through 1.5.5.7.


				     1-15
				 INTRODUCTION


				  Table 1-13
		   Symbol Table Layout for Auxiliary Chunks
				 (.SECTs only)

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	      |								  |
     |	 1    | bits 0-2    = field number for absolute program sections  |
     |	      |								  |
     |	      |	    = restriction type for relocatable program	  |
     |	      |	      sections:					  |
     |	      |								  |
     |	      |		0 = No restriction			  |
     |	      |		1 = Absolute field restriction specified  |
     |	      |		    in word 2				  |
     |	      |		2 = 12-bit absolute PC restriction in	  |
     |	      |			    word 2				  |
     |	      |		3 = Same page and field as 15-bit pointer |
     |	      |		    in word 2				  |
     |	      |		4 = Same field as 15-bit pointer in word 2|
     |	      |		    bits 4-11 = LSD number		  |
     |	      |								  |
     |	 2    | restriction for the PC according to the contents of bits  |
     |	      | 0-2 in word 1 (above).  (For .ASECTs this word is low	  |
     |	      | current location counter (PC).)				  |
     |	      |								  |
     |	 3    | LEVEL/OVERLAY:  bits 0-2 = 0				  |
     |	      |		5-7 = level number			  |
     |	      |		8-11 = overlay number			  |
     |	      |								  |
     |	 4    | bits 0-10 = unused					  |
     |	      |        11 = CONCAT keyword				  |
     |	      |	    0 = not specified				  |
     |	      |	    1 = specified				  |
     |	      |								  |
     |	 5    | Length of .FSECT without literals			  |
     |	      |								  |
     |	 6    | unused							  |
     |	      |								  |
     |	 7    | unused							  |
     ----------------------------------------------------------------------



     1.6  TABLES, STACKS, AND BUFFERS

     Table 1-14 lists the tables, stacks, and buffers contained in  MACREL.
     They  are  discussed  either in the detailed description of the module
     where they reside or in the comments of the assembly listing for  that
     module.


				     1-16
				 INTRODUCTION


				  Table 1-14
		    Summary of Tables, Stacks, and Buffers

     ----------------------------------------------------------------------
     |   Name	|  Module  |  Section |		 Description		  |
     |----------|----------|----------|-----------------------------------|
     |		|	   |	      |					  |
     |	AT	|  MACRO   |  2.13    | Actual .MACRO Argument Table	  |
     |		|	   |	      |					  |
     |	CURPAG	|  MACIO   |  2.9.8   |	Current Page Literal Table	  |
     |		|	   |	      |					  |
     |	EXPSTK	|  MACIO   |   ---    | Expression Parser Stack		  |
     |		|	   |	      |					  |
     |	FT	|  MACMAC  |  2.10.1  |	Formal (dummy) .MACRO Argument	  |
     |		|	   |	      |	Table				  |
     |		|	   |	      |					  |
     |	INPBUF	|  MACIO   |  2.8.2   |	Input Buffer			  |
     |		|	   |	      |					  |
     |	LIMTBL	|  MACINI  |  2.7.4   |	Memory Limit Table		  |
     |		|	   |	      |					  |
     |	LINBUF	|  MACIO   |  2.17.16 | Line Buffer			  |
     |		|	   |	      |					  |
     |	MACTBL	|  MACTBL  |  2.15    |	Character Branch Table		  |
     |		|	   |	      |					  |
     |	MESLIST	|  MACERR  |  2.5     |	Error Message Pointer Table	  |
     |		|	   |	      |					  |
     |	MESTBL	|  MACERR  |  2.5     |	Error Message Table		  |
     |		|	   |	      |					  |
     |	PAGE0	|  MACIO   |  2.9.8   |	Page 0 Literal Table		  |
     |		|	   |	      |					  |
     |	PTRTBL	|  FIN3	   |  2.4.1   |	Symbol Table Listing Format	  |
     |		|	   |	      | Pointer Table			  |
     |		|	   |	      |					  |
     |	OUTBUF	|  MACIO   |  2.8.14  |	Output Buffer			  |
     |		|	   |	      |					  |
     |	RADBUF	|  EXPOVR  |  2.1.1   |	Contains value of current term	  |
     |		|	   |	      |	in the current radix		  |
     |		|	   |	      |					  |
     |	STRSTK	|  MACIO   |  2.2.10  |	Input Coroutine Stream Stack	  |
     |		|	   |	      |					  |
     |	SYMTAB	|  MACINI  |  2.7.6   |	Initial Permanent Symbol Table	  |
     |		|	   |	      |					  |
     |	USRSTK	|  MACIO   |  2.29.5  |	PUSH and .POP Directives'	  |
     |		|	   |	      | Stack				  |
     ----------------------------------------------------------------------



     1.7  DEFAULT CONDITIONS

     All default operating conditions  are  explained  in  the  MACREL/LINK
								___________
     User's  Manual.  The default value for an undefined symbol is absolute
     ______________
     0.


				     1-17
				 INTRODUCTION


     1.8  ERROR AND EXCEPTION REPORTING

     Whenever  possible,  MACREL  attempts  to  continue  after  an  error.
     Therefore,  it  processes  error  calls using a JMS instruction rather
     than a JMP instruction when calling the error message processor ERROR.
     When  control  returns to the calling routine, it attempts to continue
     processing the current line.  If this is not possible,  it  scans  the
     remainder  of the line looking for an end-of-statement delimiter so it
     can parse the next line.

     MACREL's main operating concept is that assembly  should  continue  at
     all  costs.   For example, when the symbol table becomes full, further
     assembly is not possible.  Rather than terminating  operation,  MACREL
     displays   an   error   message  and  simulates  an  end-of-input-file
     condition.  This allows it to proceed to the next  pass  so  that  the
     user  can  obtain  a  partial  listing  of  the program, no matter how
     catastrophic the error.

     MACREL also displays error  messages  at  the  terminal  that  are  of
     sufficient  detail to let the user correct the error without resort to
     a listing.


































				     1-18






				   CHAPTER 2

			  DESCRIPTIONS OF THE MODULES



     This chapter contains the detailed  descriptions  of  the  modules  in
     MACREL.   They  are  presented  in  alphabetical order by module name.
     Table 2-1 lists the modules and the sections where they are described.
     Within  each module description, the various routines are described in
     order of their appearance in the source code.


				   Table 2-1
			     MACREL Module Summary

     ----------------------------------------------------------------------
     | Module |			      Description		| Section |
     |--------|-------------------------------------------------|---------|
     | EXPOVR |	Overlay to the expression processor module	| 2.1	  |
     |	      |	(MACEXP)					|	  |
     |	      |							|	  |
     | FIN0   |	Pass initialization overlay			| 2.2	  |
     |	      |							|	  |
     | FIN2   | End-of-pass overlay for passes 1, 2, and 4	| 2.3	  |
     |	      |							|	  |
     | FIN3   | End-of-pass overlay for pass 3			| 2.4	  |
     |	      |							|	  |
     | MACERR | Error message overlay				| 2.5	  |
     |	      |							|	  |
     | MACEXP | Expression processor (resident)			| 2.6	  |
     |	      |							|	  |
     | MACINI | Once-only initialization code			| 2.7	  |
     |	      |							|	  |
     | MACIO  | I/O module (resident)				| 2.8	  |
     |	      |							|	  |
     | MACLIT | Literal processor overlay			| 2.9	  |
     |	      |							|	  |
     | MACMAC |	Macro processor (overlay)			| 2.10	  |
     |	      |							|	  |
     | MACOPN |	File open routines (overlay)			| 2.11	  |
     |	      |							|	  |
     | MACORG |	Program counter (origin) processor (overlay)	| 2.12	  |
     |	      |							|	  |
     | MACRO  |	Macro processor (resident)			| 2.13	  |
     |	      |							|	  |
     | MACRTH |	Global arithmetic processor (overlay)		| 2.14	  |
     |	      |							|	  |
     | MACTBL |	Character branch table (resident)		| 2.15	  |
     ----------------------------------------------------------------------
						 (continued on next page)

				      2-1
			  DESCRIPTIONS OF THE MODULES


			       Table 2-1 (Cont.)
			     MACREL Module Summary

     ----------------------------------------------------------------------
     | Module |			      Description		| Section |
     |--------|-------------------------------------------------|---------|
     | MAC2   |	Code specific to passes 2 and 4 (resident)	| 2.16	  |
     |	      |							|	  |
     | MAC24  |	Main routines (resident)			| 2.17	  |
     |	      |							|	  |
     | MAC30  |	Code specific to passes 1 and 3 (overlay)	| 2.18	  |
     |	      |							|	  |
     | MAC3R  |	Code specific to passes 1 and 3 (resident)	| 2.19	  |
     |	      |							|	  |
     | OVRA   |	.PAGE, ZBLOCK, and .TEXT directives (overlay)	| 2.20	  |
     |	      |							|	  |
     | OVRB   | Conditional assembly directives (overlay)	| 2.21	  |
     |	      |							|	  |
     | OVRC   |	Radix control, FILENAME, DEVICE,		| 2.22	  |
     |	      |	.ENABLE, and .DISABL directives (overlay)	|	  |
     |	      |							|	  |
     | OVRD   |	Program section (.SECT) directives (overlay)	| 2.23	  |
     |	      |							|	  |
     | OVRE   |	Global declarations and .INCLUDE and .CHAIN	| 2.24	  |
     |	      | directives (overlay)				|	  |
     |	      |							|	  |
     | OVRQ   |	Block letter printer (overlay)			| 2.25	  |
     |	      |							|	  |
     | OVRR   |	Listing directives, pre-end-of-pass		| 2.26	  |
     |	      |	overlay, and .START, .JSW, .VERS, NOPUNCH, and  |	  |
     |	      |	ENPUNCH directives (overlay)			|	  |
     |	      |							|	  |
     | OVRS   |	FIXTAB and EXPUNGE directives (overlay)		| 2.27	  |
     |	      |							|	  |
     | OVRT   | FIELD directive and "pass 5 " (post-processing) | 2.28	  |
     |	      |	(overlay)					|	  |
     |	      |							|	  |
     | OVRU   |	.TITLE, .SBTTL, RELOC, .PUSH, and .POP		| 2.29	  |
     |	      | directives (overlay)				|	  |
     |	      |							|	  |
     | PAS2   |	Code specific to passes 2 and 4 (overlay)	| 2.30	  |
     ----------------------------------------------------------------------



     2.1  EXPOVR (Overlay 32)

     This module is an  auxiliary  overlay  for  the  expression  processor
     module (MACEXP).



     2.1.1  BACKL


				      2-2
			  DESCRIPTIONS OF THE MODULES


     The routine BACKL processes the backslash (\) operator.   Its  calling
     sequence is:

	  JMS BACKL
	  routine

     where:

	  routine is the address of the routine that receives characters

     BACKL performs the following operations:

	  1.  Stores the state of the symbol parser (PARSYM  in  MAC24)  on
	      the  expression  stack  (EXPRSTK)  by  saving the contents of
	      locations:  FILESW,  PDSWT,  IDKNT,  DOLFLG,  NAMPTR,  NAME1,
	      NAME2,  NAME3,  NAME4, PARSYM, UNARYM, and TERM.  This is for
	      cases where BACKL is called during a symbol parse  operation.
	      This  serves no purpose when BACKL is called while processing
	      an actual macro argument (MC in OVRX).


					  NOTE

			BACKL must save TERM  because  it  calls
			the term processor recursively to obtain
			the value of the term that  follows  the
			backslash.


	  2.  Parses a term by calling TERM.  An error results if the value
	      of the term is not absolute.

	  3.  Removes the values saved previously from EXPRSTK  to  restore
	      the context of the current invocation of TERM.

	  4.  Converts the value of the term to its representation  in  the
	      current  radix.   The  number  is  treated  as unsigned.  The
	      conversion is accomplished by dividing the term  successively
	      by  RADXWD  and  storing  the  result temporarily in a 6-word
	      buffer called RADBUF.  The  computed  digits  are  stored  in
	      reverse  order.   RADBUF  is terminated by a negative number.
	      Five divisions are  always  performed,  because  dividing  to
	      completion  could cause buffer overflow if the radix is small
	      (for example, a two).  Therefore, the  routine  returns  only
	      the low order five digits of the result.

	  5.  Scans the buffer in  a  forward  direction  ignoring  leading
	      zeros and sending the remaining characters to the appropriate
	      routine, by using the call:

		   TAD char
		   JMS I SNDRTN

	      where:

				      2-3
			  DESCRIPTIONS OF THE MODULES



		   char	      is a MACREL 6-bit code for any numeric
			      character (0 through 9)

		   SNDRTN     points to one of two routines specified by
			      the caller

	  6.  Causes SNDRTN to point to SYMSTO (MAC24)  if  called  by  the
	      symbol  parser, PARSYM (MAC24).  SYMSTO packs characters into
	      MACREL 6-bit code and places them in locations NAME1  through
	      NAME4 of the symbol table work area (MAC24).

	  7.  Causes SNDRTN to point to STORMS (MACRO)  if  called  by  the
	      actual  macro argument processor, MC (MACMAC).  STORMS stores
	      characters in macro argument space.

     The following is a list of common variables that BACKL uses:

	  LD0FLG      Leading  zero  flag.   It  is  set  to  zero  at  the
		      beginning  of  the second scan through RADBUF.  It is
		      set to a non-zero value if a non-zero digit is found.
		      Thus, a zero means a leading zero.

	  RADPTR      Points to RADBUF.

	  SNDRTN      Contains the  address  of  the  routine  that  is  to
		      receive  the  digits  (in  radix representation) that
		      followed the backslash.

	  BCKNT	      Counter that prevents  overflow  of  RADBUF.   It  is
		      initially set to -5.



     2.1.2  IDIV

     IDIV is a routine that performs 12-bit unsigned division by repeatedly
     subtracting  the  divisor  from the dividend.  The quotient is left in
     the AC and the remainder is deposited in REMAIN.  If the divisor is 0,
     an  error  message is generated and the quotient is set to 0, with the
     number becoming the  remainder.   It  tests  the  link  to  check  for
     completion.   QUO  contains  the partial quotient while the routine is
     running.

     The calling sequence is:

	  TAD dividend
	  JMS IDIV
	  12-bit address of divisor



     2.1.3  IMUL


				      2-4
			  DESCRIPTIONS OF THE MODULES


     The  routine  IMUL  performs   12-bit   unsigned   multiplication   by
     successively adding the multiplicand to itself.  The multiplier is the
     iteration count.  The temporary product resides in QUO, and the  final
     product in the AC.

     The calling sequence is:

	  TAD multiplicand
	  JMS IMUL
	  12-bit address of multiplier



     2.1.4  SNGLQQ

     The routine SNGLQQ processes the single  quote  (')  ASCII  conversion
     operator.   It  is  called by the expression processor (MAXEXP) when a
     single quotation mark occurs at  the  beginning  of  a  term.   SNGLQQ
     performs the following operations:

	  1.  Calls (QQ)GETKAR (MAC24) to get the next two characters  from
	      the input stream.

	  2.  Converts the two characters into 6-bit ASCII and  packs  them
	      into  one  word.   The  first  character  resides in the most
	      significant six bits, and the second character in  the  least
	      significant six bits.

	  3.  Stores the result as an absolute value in TRMABS.

	  4.  Generates an error message and aborts the  statement  if  two
	      characters do not follow the single quote.

	  5.  Calls (QQ)GETCHR (in MAC24) so that the first character after
	      this term becomes the current character.


					  NOTE

			SNGLQQ does not zero the  relative  part
			of  the  term.  Instead, MACEXP performs
			this task when SNGLQQ returns control to
			it.

	  6.  Returns to the calling routine with the two 6-bit  characters
	      packed in the AC.



     2.1.5  UPAROQ

     The routine UPAROQ implements  the  temporary  (local)  radix  control
     command  constructs:  B, D, and O, and the control character construct


				      2-5
			  DESCRIPTIONS OF THE MODULES


     ".  It is called  from  the  expression  processor  (MACEXP)  when  it
     encounters an uparrow (^) at the beginning of a term.

     UPAROQ performs the following operations:

	  1.  Saves the current  radix,  residing  in  RADXWD  (MAC24),  by
	      storing it in HLDRAD.

	  2.  Reads the next character, and takes action according to which
	      one of the following situations obtains:

	      a.  If the routine finds no character, it assumes the end  of
		  line  was reached, generates an error message, and aborts
		  the statement.

	      b.  If it finds a character other than B,  D,  O,  or  ",  it
		  generates  an error, sets the result (TRMABS, TRMREL, and
		  TRMCOD) to absolute 0, and returns to the caller.

	      c.  If the routine finds B, D, O, or ", it  branches  to  the
		  appropriate entry point.

		       Character    Entry Point      Condition

			   B	       BINOVR	     Binary radix
			   D	       DECOVR	     Decimal radix
			   O	       OCTOVR	     Octal radix
			   "	       CNTCON	     Control Character


					  NOTE

			Decimal radix,  indicated  by  a  number
			that ends with a period (decimal point),
			is detected by  GETNUM  (MACEXP),  which
			sets DFLG to 0.

	  3.  Sets RADXWD to 10, 8, or 2 respectively, and  passes  control
	      to  the  radix  override  portion  of  the  code.   This code
	      determines whether the next character  is  a  digit.   If  no
	      digit  follows,  it generates an error message and aborts the
	      statement.  If a digit is present, it calls  GETNUM  (MACEXP)
	      to  parse  the  number  in the new (local) radix.  This value
	      becomes the absolute part of the resulting term.

	  4.  Restores the original radix, and checks to determine  if  the
	      current radix conflicts with the original radix.  If there is
	      a conflict (the number ended in a period [decimal point]  and
	      the  radix  override  option is not D), it generates an error
	      message.  (GETNUM indicates that  the  number  ended  with  a
	      period  by  setting DFLG to 0.) No error is generated if an D
	      preceded the number.  (This is redundant, but  not  an  error
	      condition.)


				      2-6
			  DESCRIPTIONS OF THE MODULES


				     NOTE

		   TENFLG always contains a 0, except  when
		   a  D is detected-in which case it is set
		   to 4000.  This indicates whether or  not
		   decimal radix is in effect so that radix
		   conflicts can be detected.

		   UPAROQ does not zero the  relative  part
		   of  the  term.  Instead, MACEXP performs
		   this task when UPAROQ returns control to
		   it.

		   The CNTCON routine does  not  reside  in
		   this  module because it shares code with
		   the DBLQ routine in MACEXP.



     2.2  FIN0 (Overlay 10)

     FIN0 is the pass initialization overlay.  At  the  beginning  of  each
     assembly  pass, control returns to this module through its entry point
     NEXTT.


				     NOTE

		   The call to this module may be  hard  to
		   locate  in  the  listing and will not be
		   found in  the  cross-reference  listing.
		   This  is because the call does not refer
		   to the entry point NEXTT by  name.   The
		   call  occurs  at symbol INHAND (location
		   NEX+3) in MAC24.



     2.2.1  NEXTT

     The routine NEXTT is the entry point to this module.  It is called  at
     the beginning of each pass to perform the following tasks:

	  1.  Calls IONIT2 (MACIO in Field 1) to perform  preliminary  pass
	      initialization.

	  2.  Zeros location  01400  to  indicate  that  the  Pass-Specific
	      Overlay Area is unoccupied.

	  3.  Loads the  pass-specific  overlay,  using  either  MAC30  for
	      passes 1 and 3, or PAS2 for Passes 2 and 4.

	  4.  Increments the pass number (PASS in MAC24), and  branches  to
	      OPEN1,  OPEN2,  OPEN3, OPEN4, or FIN5 depending on which pass

				      2-7
			  DESCRIPTIONS OF THE MODULES


	      is beginning.  Each of these routines branches to  REIT  when
	      completion.   (If  a  routine  decides  to  abort  a pass, it
	      branches to  NEXTT  to  proceed  with  the  next  pass.   The
	      overlays are loaded redundantly when this happens.)



     2.2.2  OPEN1

     The routine OPENl opens the  table  of  contents  (TOC)  file  at  the
     beginning  of  Pass  1  by  calling  OPENTC (MACOPEN, Overlay 33).  On
     completion, control returns to REIT.



     2.2.3  OPEN2

     OPEN2 is a routine that calls OPEN (MACOPEN, Overlay 33) to  open  the
     binary  output file at the beginning of pass 2.  The default file name
     extension is .RB.  OPEN2 then stores the starting block number of  the
     file that resides in OUTLOC (MACIO) by depositing it in RBFILE (MACIO)
     in case the user requested chaining to  LINK.   This  is  because  the
     Command  Decoder's  output  file  table  contains  file  names  but no
     starting addresses.  Upon completion, control returns to REIT.  If the
     user  did  not  specify  a binary file, OPEN2 skip pass 2 by branching
     back to NEXTT.



     2.2.4  OPEN3

     OPEN3 is a routine that is called at the beginning of pass 3  to  open
     the  listing  file,  print  the  block  letter  heading, and print the
     table-of-contents.  It performs the following operations:

	  1.  Loads zeros into location LOCOFF (MACIO).  LOCOFF is used  by
	      the  OPEN (MACOPN) routine.  Whenever OPEN is called, it adds
	      the contents of LOCOFF to the starting block  number  of  the
	      file to establish the block where output is to begin.  During
	      pass 2 LOCOFF contains a value that is equal to the number of
	      blocks  in  the  Loader  Symbol  Dictionary (LSD) area of the
	      binary file.  This offset allows OPEN to skip over the file's
	      LSD area.  This result is not desirable during pass 3.

	  2.  Calls OPEN (MACOPEN) to open the listing file.   The  default
	      file  name  extension  is  .LS.   It  sends characters to the
	      output file in 8-bit character mode.

	  3.  (if no listing file was specified) Skips Pass 3 by  branching
	      back to NEXTT.

	  4.  (if a listing file was specified) Checks to see if  the  user
	      specified  the  /B  option.  If /B was not specified, control
	      branches to CPYTOC to print the  table-of-contents  (TOC)  in

				      2-8
			  DESCRIPTIONS OF THE MODULES


	      the  listing  file.   If  the  /B option was specified, OPEN3
	      proceeds to print a block letter heading at the  top  of  the
	      listing before branching to CPYTOC.

	      Each block letter  consists  of  a  number  of  basic  letter
	      blocks.  The basic letter block is the fundamental structural
	      element for creating block letters.  It consists of an  array
	      of  identical letters.  The width of the array varies between
	      1 and 3 letters, depending on the width  of  the  page.   The
	      horizontal  image  area  for a block letter is 6 basic letter
	      blocks wide (5 plus a space).  By changing the width  of  the
	      basic  letter  block,  the  overall width of the block letter
	      heading can be altered.  Since a file name can contain up  to
	      6 letters, a minimum of 36 character positions is required on
	      the output device to contain a block letter heading.

	  5.  Adjusts the block letter width relative to the width  of  the
	      listing  device  page  by  dividing  the  column width of the
	      listing device (WIDTH in MAC24) by 44(octal).  The  resulting
	      value  determines  the width of a basic letter block as shown
	      in Table 2-2.  If the result of the division is 0, the output
	      device's  width  is too small to print a block letter heading
	      and  control  branches  directly  to  CPYTOC  to  print   the
	      table-of-contents.   If  the  result is greater than 3, OPEN3
	      ignores it and maintains a basic letter block width of 3  for
	      devices wider than 108 columns.


				   Table 2-2
			 Basic Letter Block Widths vs
			 Listing Device Column Width

     ----------------------------------------------------------------------
     |	Listing Device Width		  | Basic Block Width		  |
     |------------------------------------|-------------------------------|
     |		1-35			  |    0 letters		  |
     |		36-71			  |    1 letter			  |
     |		72-107			  |    2 letters		  |
     |	     greater than 107		  |    3 letters		  |
     ----------------------------------------------------------------------

	  6.  Loads Overlay 21, the  block  letter  printer  BLKLET  (OVRQ)
	      and  Overlay  24,  MACREL's  fish  caricature  printer  BINFO
	      (OVRQ).

	  7.  Calls BLKLET to print the  block  letters.   (It  passes  the
	      width  of  the  basic letter block as a negative value in the
	      AC.)

	  8.  Calls BINFO to print the fish  caricature,  MACREL's  version
	      number, and the number of errors (if any).

	  9.  Calls CPYTOC to  send  the  table-of-contents  (TOC)  to  the
	      listing file.  Thereafter, control returns to REIT.

				      2-9
			  DESCRIPTIONS OF THE MODULES


     2.2.5  OPEN4

     OPEN4 is a routine that is called at the beginning of pass 4  to  open
     the   cross-reference   (KREF)   file.    It  performs  the  following
     operations:

	  1.  Loads zeros into location LOCOFF (MACIO).  LOCOFF is used  by
	      the  OPEN (MACOPN) routine.  Whenever OPEN is called, it adds
	      the contents of LOCOFF to the starting block  number  of  the
	      file to establish the block where output is to begin.  During
	      pass 2 LOCOFF contains a value that is equal to the number of
	      blocks  in  the  Loader  Symbol  Dictionary (LSD) area of the
	      binary file.  This offset allows OPEN to skip over the file's
	      LSD area.  This result is not desirable during Pass 4.

	  2.  It calls OPEN (MACOPN) to open the KREF output  file.   (OPEN
	      uses  the default extension .KF if one does not already exist
	      in the Command Decoder's output file table.) The output  mode
	      is 12-bit binary.

	  3.  Takes  action  according  to  which  one  of  the   following
	      circumstances obtains:

	      a.  If the user specified the /C option and did not  enter  a
		  device  or  file  name  as  the  third (KREF) output file
		  specification, OPEN4 inserts  the  default  specification
		  SYS:KF.TM  into  the  appropriate  position  in  the OS/8
		  Command Decoder's output file table.

	      b.  If the user did not specify the /C option or a KREF  file
		  specification,  OPEN4  skips  pass 4 by branching back to
		  NEXTT.

	      c.  If a KREF file was specified, OPEN4 stores  the  starting
		  block number of the KREF output file (OUTLOC in MACIO) in
		  location KFFILE (MACIO).  This information  in  necessary
		  if  the  user  requested  chaining  to  KREF,  since  the
		  starting block number is not stored in the file's Command
		  Decoder's file table.

	  4.  Upon completion, control returns to REIT.



     2.2.6  FIN5

     The routine FIN5 determines whether to  return  control  to  the  OS/8
     Monitor or to chain to KREF or LINK.  It is called after all requested
     passes are processed.  If the user selected the /L, /G, or /C options,
     FIN5  passes  control  to location LNKCHN in Overlay 24 (OVRT) to scan
     the options, modify the command decoder area, and set up the chain  to
     KREF  or  LINK  as specified.  If none of these options was specified,
     MACREL operation is complete and FIN5  returns  control  to  the  OS/8
     Monitor by branching to absolute location 7605.

				     2-10
			  DESCRIPTIONS OF THE MODULES


     2.2.7  AINIT

     The routine AINIT sets initial values before starting each  pass.   It
     performs the following operations:

	  1.  CONCNT to 0,  to  indicate  that  there  are  no  conditional
	      directives in effect.

	  2.  PAGENO (listing page number) to 0.

	  3.  LINENO and LINEN2 (listing line number) to 0.

	  4.  RELOK to 0, to inhibit RELOC directive.

	  5.  ERKNT (error counter) to 0.

	  6.  Increments PPASS (physical pass number) by 1 each time a pass
	      is actually begun.  Notice that PPASS is different from PASS,
	      which contains the logical pass number.   The  physical  pass
	      number  is  used  by  the  error processor (MACERR module) to
	      determine whether or not an error message should  be  printed
	      at the terminal.  (Many error messages only appear during the
	      first physical pass during which they occur).

	  7.  Deposits spaces in the subtitle line locations (SUBTL through
	      SUBTL+(SUBLEN-1)) in MAC24.

	  8.  Sets QUAL to 0, to indicate that a local symbol  block  (LSB)
	      is not being processed.

	  9.  Sets CURFLD (current field) to 0.

	 10.  Sets LITPAG (Page of the current page literals) to page 200.

	 11.  Sets PUNFLG to 0, to enable binary output (punching).

	 12.  Sets LITSCT to 0.

	 13.  Sets CLTLOC and ZLTLOC to 0 to indicate that no current  page
	      or Page 0 literals have been detected.

	 14.  Sets EXTPC to 0, to indicate that MACREL's current location
	      counter (PC) is not external (in case the last pass ended by
	      changing the current location counter to the value of an
	      external symbol).

	 15.  Calls UNNAM (MAC2) to set up the default program  section  to
	      be an unnamed absolute program section.

	 16.  Sets the initial values of ENABWD and LISTWD as the  contents
	      of   INIENAB   and   INILST  (the  initial  ENABLE  and  LIST
	      conditions) respectively.  You can patch these  locations  to
	      different  values  if  you want to establish your own initial
	      conditions.

				     2-11
			  DESCRIPTIONS OF THE MODULES


	 17.  Sets the default radix to be octal by depositing  10  (octal)
	      in RADXW.

	 18.  Deposits 0 in OLDSCT, to indicate that there was no  previous
	      .SECT  directive  in  effect.   (This  prevents  a  user from
	      starting with a .SECT directive.)

	 19.  Deposits 0 in ZSECTN to clear the name of any page 0  literal
	      program section.

	 20.  Deposits 0 in BNFLAG and PCFLAG so that no binary or  current
	      location  counter  (PC)  value will be printed in the listing
	      unless requested.

	 21.  Sets MACLEV (macro nesting level) to 0.

	 22.  Deposits 0 in LNKGEN, to indicate that a link  has  not  been
	      generated yet.

	 23.  Calls  IOINIT  (MACIO  in  Field  1)   to   perform   further
	      initialization.  (This code resides in MACIO [Section 2.8] to
	      reduce the number of globals in this module.)



     2.2.8  CPYTOC

     The routine CPYTOC copies the table-of-contents (TOC) from the scratch
     blocks  on  the system device (SYS:) to the listing file.  It performs
     the following operations:

	  1.  Checks to see if  a  table-of-contents  was  created  on  the
	      previous  pass.   By  examining  the  contents  of the .SBTTL
	      directive counter SBTKNT  (MAC24).   If  SBTKNT  contains  0,
	      there  are no .SBTTLs and CPYTOC exits.  Otherwise, it checks
	      to see if the output buffer is  empty.   (The  output  buffer
	      might  not  be  empty  if  the  block letter heading was just
	      printed and the last buffer has not been written yet.) If the
	      output  buffer  is  not empty, CPYTOC sends it to the listing
	      file by padding the buffer with  NULs  (repetitive  calls  to
	      (QQ)LISTER(MAC3R) with AC=0000).

	  2.  Begins the copy operation, starting at a  block  boundary  to
	      avoid a longer listing buffer.


				     NOTE

		   The extra  zeros  will  not  affect  the
		   block  length  of the file.  Any program
		   that  reads  this  file  should  discard
		   these NULs.



				     2-12
			  DESCRIPTIONS OF THE MODULES


	  3.  Copies the blocks directly from the scratch area on SYS:   to
	      the  listing  file.   It  reads  them  by making calls to the
	      system handler.   It  writes  them  out  by  calling  PUTBUF.
	      TOCSIZ specifies the number of blocks to transfer.


				     NOTE

		   If the system  handler  detects  a  read
		   error,  it is fatal.  This causes MACREL
		   to halt because there may be no  way  to
		   recover.



     2.2.9  REIT

     The routine REIT performs file initialization once an output  file  is
     opened.   It  calls AINIT to initialize variables, then passes control
     to LOOP (MAC24).



     2.2.10  IOINIT

     The routine IOINIT, though logically part of FIN0, resides in Field  1
     in module MACIO.  It performs the following pass initialization steps:

	  1.  Marks the stream input routines:  ORET, ZRET, MRET, and  RRET
	      as being unused.

	  2.  Initializes  AT1  (MAC24),  the  main  macro  argument  table
	      pointer.

	  3.  Sets OV1 to 0 to indicate that the number  of  nested  macros
	      does not exceed the nesting limit.

	  4.  Empties  the  stream  stack  by  zeroing  location   STRSTK+1
	      (MACIO).

	  5.  Calls SWITCH to establish ZGET as the  initial  stream  input
	      coroutine.   (This  coroutine  does nothing but return CTRL/Z
	      codes.)

	  6.  Calls SWITCH to establish  OGET  as  the  next  stream  input
	      coroutine.   This is a protective device to force a return to
	      ZGET  in  the  event  an  internal  error  in  the  coroutine
	      switching  mechanism  causes  stream stack underflow past the
	      initial OGET.

	  7.  Sets DVNO to 0 to signify to the OGET coroutine that no input
	      file  is open yet.  Thus, when the first character is sent to
	      OGET, READOS will be called, which in turn will branch to EOS
	      (MAC24) to read the first OS/8 input file.

				     2-13
			  DESCRIPTIONS OF THE MODULES


     2.2.11  IONIT2

     The routine IONIT2, although logically part of FIN0,  resides  in  the
     MACIO   module   in   Field   1.    It  performs  the  following  pass
     initialization steps:

	  1.  Zeros FILENO to indicate that the first input  file  has  not
	      been read.

	  2.  Sets INI.EN to 0 to indicate that no input file  blocks  have
	      been read.

	  3.  Deposits the pointer to the first input file specification of
	      the CD area in INPTR.



     2.3  FIN2 (Overlays 12 and 14)

     The FIN2 module consists of two overlays:  12 and  14.   They  perform
     general-purpose, end-of-pass tasks such as:  writing the Loader Symbol
     Dictionary (LSD) to the output file,  emptying  buffers,  and  closing
     files.   They are called at the end of passes 1, 2, and 4. Overlay 12,
     the main overlay, resides in the Extremities  Overlay  Area;   Overlay
     14,  the  auxiliary  overlay  resides  in  the Directives Overlay Area
     during pass 2.



     2.3.1  Unlabeled Routine

     This is an unlabeled routine that consists of  the  code  that  begins
     with  the  (overlay)  number 12 and ends at the label LSDOUT. There is
     no label because this routine is entered by a  direct  branch  to  the
     start of the overlay area.  It performs the following tasks:

	  1.  Zeros LSDNUM.  This step provides coding consistency. It  can
	      be  removed  without effect, since the contents of LSDNUM are
	      initially 0 when the overlay is loaded.

	  2.  (if this is the end of pass 2)

	      a.  Sends an end-of-text code (a word containing NUL with a 3
		  as the flag field value) to the binary file.

	      b.  Dumps the last buffer of binary code by calling ZPAD.

	      c.  Closes the binary file by calling CLOSO (MACIO).

	      d.  Calls FINIO (MACIO).

	      e.  Loads  the  extension  overlay  (Overlay  14)  and  calls
		  subroutine LSDINI.


				     2-14
			  DESCRIPTIONS OF THE MODULES


	  3.  Scans the symbol table according to the following conditions:

	      a.  If the symbol belongs to  the  Loader  Symbol  Dictionary
		  (LSD),  calls  LSDOUT.  A symbol belongs in the LSD if it
		  is a program section name (flag bits 6-8 are nonzero), or
		  if  it  is  EXTERNAL, ZTERNAL, ENTRY, or GLOBAL (flag bit
		  9=1).

	      b.  If the symbol is a  program  section  name,  the  routine
		  deposits zeros in SYMVAL (high current location counter).

	      c.  If the symbol is an .ASECT name, the routine sets word  2
		  of  the auxiliary chunk (low current location counter) to
		  -1 to indicate that the lowest location counter value  is
		  not yet determined.

	  4.  (if this is the end of pass 1) Estimates the number of blocks
	      required  to  store the LSD entries in the binary output file
	      and stores this value in LOCOFF (MACIO).  (The assumption  is
	      that all LSD entries are defined during pass 1.) It does this
	      by performing the following sequence:

	      a.  Computes the maximum  size  that  the  LSD  could  be  by
		  multiplying  the  number  of  LSD  entries  (LSDNUM) by 6
		  (since each LSD entry is not more than 6 words long).

	      b.  Adds this value to the maximum length of the LSD  preface
		  (currently assumed to be 40 [octal] words long).

	      c.  Rounds this result up to the  next  multiple  of  400  (a
		  block boundary) to produce the maximum expected length of
		  the LSD portion of the binary file.

	      d.  Stores this value in LOCOFF (MACIO).  The  OPEN  (MACOPN)
		  routine  uses  this  value  as an offset to determine the
		  first block of the binary file where it can begin storing
		  the LSD text.

	      The routine stores the text portion of the binary file before
	      the  LSD,  because  the  exact  lengths  of  floating program
	      sections that contain current page literals are unknown.


				     NOTE

		   Because  the  number  of  current   page
		   literals  may  decrease  due  to literal
		   sharing, the length of .FSECTs cannot be
		   determined until the end of pass 2.


	  5.  (if  this  is  the  end  of  pass   1   and   there   is   no
	      table-of-contents  [SBTKNT=0]) Branches  to  NEX  (MAC24)  to
	      proceed to the next pass.

				     2-15
			  DESCRIPTIONS OF THE MODULES


	  6.  Sends the last buffer to the output file and closes the file.
	      Two  different procedures are used depending upon whether the
	      output mode is binary or ASCII.

	      a.  If the output mode is ASCII, (that  is,  an  odd-numbered
		  pass), the routine:

			 i.    Transmits the last buffer to the output file
			       by  sending  a  bufferful  of CTRL/Zs to the
			       listing file ( (QQ)LISTER in  MAC3R).   This
			       guarantees  that  the  last  buffer  will be
			       written out and  that  the  output  file  is
			       terminated with a CTRL/Z.

			 ii.   Stores the length (in blocks) of the  output
			       file  contained  OUTSIZ  (MACIO)  in  TOCSIZ
			       (MAC24).  This information is used when  the
			       table  of  contents is copied to the listing
			       file at the start of pass 3.

			 iii.  Passes control to  NEX  (MAC24)  to  proceed
			       with the next pass.

	      b.  If the output mode is binary (that is,  an  even-numbered
		  pass),  and  if  this  is  also  the  end  of pass 2, the
		  routine:

		  Calls ZPAD to force the last buffer to be transmitted  to
		  the  output  file  and  to  pad the unused portion of the
		  Loader Symbol Dictionary (LSD) area in the file with NULs
		  (It could be that the length originally estimated for the
		  LSD  area  was  too  short.   For  example,  if  the file
		  contained  a  large  number  of  external  symbols.)  The
		  routine  writes  blocks  of NULs up to, but not including
		  the first text block.  The block  number  for  the  first
		  text  block  is stored in TXTBLK (MACIO).  If this is the
		  end of Pass 4, the routine calls Z PAD once to  dump  the
		  buffer.   Then  it  calls CLOSO (MACIO) to close the KREF
		  file.

	  7.  Control transfers to NEX (MAC24) to begin the next  pass  (if
	      there are any more).



     2.3.2  LSDOUT (Overlay 12)

     The subroutine LSDOUT sends the Loader Symbol Dictionary  (LSD)  entry
     information to the LSD portion of the binary output file.  It performs
     the following tasks:

	  1.  Increments the LSD number (LSDNUM) by 1, to maintain a  count
	      of  the  number  of  LSD entries.  LSDNUM also represents the
	      number of  the  current  LSD  entry.   The  LSD  entries  are

				     2-16
			  DESCRIPTIONS OF THE MODULES


	      numbered  and  are  sent  to  the binary file in alphabetical
	      order.  This is convenient for maintenance purposes, but  not
	      necessary for proper LINK operation.

	  2.  Inserts the LSD number for the current symbol  (LSDNUM)  into
	      bits  -11 of its QUAL word in the symbol table.  Any previous
	      contents of this field are lost.  LSDOUT stores the LSD entry
	      number,  because  the  LSD entry is referred to by its number
	      during output to the .RB file.

	  3.  Exits to FIN2 if this is not pass 2.

	  4.  Sends the 3 words containing the LSD entry's  name  by  using
	      PUTBIT (PAS2).

	  5.  Computes the type code used by  LINK  to  identify  this  LSD
	      entry   and  stores  it  temporarily  in  LTYPE.   Table  2-3
	      specifies these codes.


				   Table 2-3
			     LSD Entry Type Codes

			  --------------------------
			  |  Code     |	Entry Type |
			  |-----------|------------|
			  |	1     | .SECREF	   |
			  |	2     | .RSECT	   |
			  |	3     | .RSECT	   |
			  |	4     | .FSECT	   |
			  |	5     | .DSECT	   |
			  |    10     | .XSECT	   |
			  |    11     | .ZSECT	   |
			  |    14     | .GLOBAL	   |
			  |    15     | .ZTERNAL   |	
			  |    16     | .EXTERNAL  |
			  --------------------------


	  6.  Sends the type code to the LSD.  The code resides in the  low
	      order  4  bits  of  the  12-bit  word  (bits 8-11), while the
	      high-order 8 bits (bits 0-7) contain the LSD entry number  of
	      the  entry  that  this entry is relative to.  This address is
	      derived from the 15-bit pointer in the SYMSCT  (MAC24)  entry
	      for this LSD entry as follows:

	      a.  If this symbol is not a program section name  and  SYMSCT
		  is 0, it must be an EXTERNAL or ZTERNAL symbol.  The high
		  order 8 bits of the word are set to 0.

	      b.  If SYMSCT is a program section  name,  the  high-order  8
		  bits  must  contain  the restriction type as specified by
		  the high order 3 bits of the QUAL word (MAC24)  for  this


				     2-17
			  DESCRIPTIONS OF THE MODULES


		  LSD  entry.   (Refer to the MACREL/LINK User's Manual for
					      _________________________
		  the definition of the LSD restriction types.)

	  7.  Sends the program section  length  to  the  LSD  (unless  the
	      symbol  is  XTERNAL  or  ZTERNAL).   Except  for .ASECTs, the
	      length is stored in the SYMVAL  (MAC24)  word  for  this  LSD
	      entry.   If  the  LSD  entry  is an .ASECT, the length of the
	      .ASECT is  obtained  by  subtracting  its  low  PC  (location
	      counter) value from its high PC value (SYMVAL).

	  8.  It returns control to the caller  if  the  symbol  is  not  a
	      program section name.  Otherwise, it continues with step 9.

	  9.  Sends the restriction word to the LSD.  The word is  the  LSD
	      number  of  the  symbol  table  entry specified by the 15-bit
	      pointer in word 2 of the auxiliary .SECT chunk  (see  Section
	      1.5.5.8)  for  the  current  LSD  entry.   If the entry is an
	      .ASECT, there is no restriction code and the field number  of
	      the .ASECT is sent instead.

	 10.  Sends the LEVEL/OVERLAY word (word 3 of the  auxiliary  .SECT
	      chunk) to the LSD if the program section is an overlay.



     2.3.3  ZPAD (Overlay 12)

     This subroutine inserts 400 (octal) NULs into the page buffer to force
     the current contents of the page buffer to be sent to the output file.



     2.3.4  LSDINI (Overlay 14)

     The routine LSDINI sends the Loader Symbol  Dictionary  (LSD)  Preface
     items  to  the  binary  output  file by performing successive calls to
     (QQ)PUTBIT (MAC2) via PUTHDR.  (See the MACREL/LINK User's Manual  and
					     _________________________
     the program listing for more information on the LSD Preface.)

     The preface  items  reside  in  packets  within  LSDINI.   Their  form
     corresponds  approximately to that used for the external (binary file)
     preface.  Each packet begins with a negative number that specifies the
     number  of  words  in the packet (including the count word).  The next
     word in the packet is the item title  code  for  this  preface  entry.
     (See   MACREL/LINK  User's  Manual  for  the  code  definitions.)  The
	    ___________________________
     remaining words in the packet contain the preface item data itself.

     LSDINI sends the first five packets as a group to the output file.  It
     sends  the  remaining  packets  individually  to the output file.  The
     number of packets being sent is passed to PUTHDR as a  negative  value
     in the AC.

     For  selected  packet   entries,   LDSINI   performs   the   following
     computations before sending them to the output file:

				     2-18
			  DESCRIPTIONS OF THE MODULES


	  1.  Obtains the current date from OS/8 and inserts  it  into  the
	      current  date packet.  This packet is 2 words long so that it
	      can contain dates after 1977.  LSDINI obtains the  additional
	      date bits location 07777 and inserts the entire word into the
	      packet.

	  2.  Inserts the page number into the  page  number  packet.   The
	      page  number  is  the contents of PAGENO (MAC24) plus 2.  The
	      increment of 2 is necessary to account for the fact that  the
	      symbol  table is  considered to be a page.  LINK does not use  
	      this information.

	  3.  Obtains the Job Status Word (JSW) from location JSW  (MAC24).
	      It sends the job status word packet to the binary file if the
	      .JSW directive is encountered;  JSWKEY (MAC24 is zero.)

	  4.  Sends the starting address packet to the output file  if  the
	      .START  directive  was  encountered;  STARTK (MAC24) is zero.
	      LSDINI computes one of the following item  title  codes  from
	      the contents of STARTR (MAC24):


		  Code		 Meaning

		    1    Starting address is absolute

		    2    Address is relocatable


	      If the contents of STARTR  are  less  than  10  (octal),  the
	      starting  address  is  absolute  and this number is the field
	      number.  Otherwise, the starting address is  relocatable  and
	      this  number is a 15-bit pointer to the relative part.  START
	      (MAC24) contains the entire absolute address (code  =  1)  or
	      the absolute part of the relative address (code = 2).
	
	  5.  Obtains   the   user-specified   version   number   (.VERSION
	      directive)  from  UVER  (MAC24).   LINK  does  not  use  this
	      information.

	  6.  Obtains the  current  patch  level  of  MACREL  from  PTCHLOC
	      (HEADING in MAC24).



     2.3.5  FINIO (Macio)

     The FINIO subroutine reinitializes the binary  output  file's  control
     parameters.   This  allows  FIN2  to send the Loader Symbol Dictionary
     (LSD) preface and data to the area reserved for it at the beginning of
     the  binary output file.  Remember that the binary data (text) is sent
     to the output file first and the file  is  closed.   FIN2  then  calls
     routines  that  send  the  LSD  directly  to the file via calls to the


				     2-19
			  DESCRIPTIONS OF THE MODULES


     device handler.  The file is not explicitly opened via a call  to  the
     USR.

     Although logically part of FIN2, FINIO resides in MACIO due  to  space
     limitations.

     FINIO is called by FIN2 after it has closed the  binary  output  file.
     It performs the following tasks:

	  1.  Stores OUTLOC, which is the  starting  block  of  the  binary
	      file,  in  OUTREC  so  that  the  LSD  will  be stored at the
	      beginning of the binary file.

	  2.  Stores zeros in OUTSIZ and HOLSIZ to indicate to  the  output
	      routine  (PUTBUF  in  MACIO) that there is enough room in the
	      output file.

	  3.  Initializes the output buffer pointer (OPTR1)  to  the  first
	      location in the output buffer (contents of OUTBUF+1 ).

	  4.  Zeros FLGFLG to indicate that no flag field  is  to  be  sent
	      with the LSD.

	  5.  Zeros HDRWRD to specify in the block header that this  is  an
	      LSD block.  (0 means LSD, 4000 means text.)



     2.4  FIN3 (Overlays 11 and 13)

     FIN3 formats the symbol table printout, sends it to the listing  file,
     and closes the listing file.  It is called at the end of pass 3.

     The module consists of two overlays:  Overlay 13,  the  main  overlay,
     loads  into  the  Extremities Overlay Area;  Overlay 11, the auxiliary
     overlay, loads into the Directives Overlay Area.

     FIN3 is segmented  into  subroutines  primarily  because  of  boundary
     restrictions  on  the  PDP-8's  memory pages (most of the routines are
     called only once).  Consequently,  the  following  description  treats
     FIN3 as if it were a single logical entity.



     2.4.1  Unlabeled Routine (Overlay 11)

     This is an unlabeled routine that consists of  the  node  that  begins
     with  the overlay number 11 and ends at the label STPRNT.  It performs
     the following tasks:

	  1.  Loads the extension overlay (Overlay 11) into memory.

	  2.  Sets LISTWD to 0 to prevent the  creation  of  a  listing  by
	      overriding any program-initiated request.

				     2-20
			  DESCRIPTIONS OF THE MODULES


	  3.  Scans all the buckets, and links and creates a  single  large
	      bucket  (Bucket A) that contains all the symbol table entries
	      in alphabetical  order.   This  improves  the  efficiency  of
	      printing  the symbol table although pass 4 processing becomes
	      somewhat more inefficient.  Since the  bucket  pointers  that
	      follow   Bucket  A  are  still  present,  pass  4  efficiency
	      decreases only when the symbols that are added during pass  4
	      are  processed.   Notice that the permanent symbols remain in
	      the chain, because the chain must be intact for pass 4.

	  4.  Calculates the number of columns of symbol table  entries  to
	      print  by  adding 8 to WIDTH (number of columns on the output
	      device) and then dividing the result by  32  (decimal).   The
	      remainder  is  the  number of columns.  Since not more than 7
	      columns are allowed, the routine takes the result  modulo  8.
	      If  the number is 0, it uses 1 column.  Otherwise, it uses up
	      to 7 columns.  It stores the number of columns  to  print  in
	      COLNUM.

	  5.  Formats each page so that the symbol  table  entries  can  be
	      printed  in  alphabetical order and in columns rather than in
	      rows.  To do this, it  creates  an  auxiliary  array,  called
	      PTRTBL  which, though dimensioned at 8, can contain from 1 to
	      7 pointers;  one pointer for each column of the page.

	      As an example, the third pointer in PTRTBL is the pointer  to
	      the  chunk  that contains the first symbol name to be printed
	      at the top of the third column in  the  listing.   A  pointer
	      value  of  0  means  that  there  is no item to print in this
	      position.

	      It sets up these pointers as follows:

	      a.  Scans the symbol table beginning with the first chunk  to
		  be printed on the current page.

	      b.  Maintains, during the scan, a  count  of  the  chunks  to
		  determine which chunk will begin the next column.

	      c.  Stores the pointer to the 55th chunk in PTRTBL  when  the
		  chunk count reaches 54 (decimal).

	      d.  Ignores, during the count, permanent,  FIXTAB,  or  local
		  symbols  (bits  2  or  4  set  to 1 in their flag words).
		  These symbols are not  to  appear  in  the  symbol  table
		  listing.

		  (Notice that the last chunk computed is the  first  chunk
		  to be printed on the next page.  Its pointer is stored in
		  SYMNUM, not in PTRTBL.)

	      e.  Waits until a full page of pointers is set up  in  PTRTBL
		  and  stores  a  0 as the final entry (which is why PTRTBL


				     2-21
			  DESCRIPTIONS OF THE MODULES


		  has room for 8 entries).  It then calls STPRNT  to  print
		  this page of the symbol table.

	  6.  Passes control to location DLUP to format and print the  next
	      page  after  the  page  is  printed,  and  if there are still
	      symbols left to print.

	  7.  Inserts a CTRL/Z into the buffer when there are no more pages
	      to  print,  it fills the remaining buffer space (less 1) with
	      NULs to send the  contents  of  the  buffer  to  the  listing
	      device.

	  8.  Calls CLOSO (MACIO) to close the listing file.

	  9.  Branches to NEX (MAC24) to proceed to the next pass.



     2.4.2  STPRNT (Overlay 11)

     The routine STPRNT prints  a  physical  page  of  symbol  table  text.
     Pointers  in  PTRTBL  point  to the symbol table chunks containing the
     symbols that begin the top of each listing  column.   STPRNT  performs
     the following tasks:

	  1.  Calls NEWPAG (MAC3R) to begin a new page, and increments  the
	      sub-page number (SUBPAG) by 1.

	  2.  Loops 54 (decimal) times, once for each row (line) of text on
	      the  page.  During each iteration, it scans PTRTBL to get the
	      chunk pointers for each symbol in the row.  For each  column,
	      it performs the following tasks:

	      a.  Branches to ENDROW if the chunk pointer is 0  (end-of-the
		  row).

	      b.  (if the chunk pointer is not 0)  Copies  the  information
		  for  that  symbol  into the symbol table work area (NAME1
		  through QUAL in MAC24) and calls PRN to  print  the  name
		  the symbol.

	      c.  Prints a TAB, then calls XPRINT to print  the  additional
		  information associated with this symbol name.

	      d.  Zeros the symbol's current location counter (PC)  if  the
		  entry is a program section name.  If it is an .ASECT, the
		  routine sets the symbol's low PC to -1.

	      e.  Replaces the current chunk pointer in  PTRTBL,  with  the
		  pointer to the next chunk for this column.  It skips both
		  local and permanent symbols.  It inserts 0 if  there  are
		  no more chunks for this column.

	      f.  Advances to the next column.

				     2-22
			  DESCRIPTIONS OF THE MODULES


	  3.  Exits if it encounters a 0 as  the  first  entry  in  PTRTBL,
	      because  there  are  no  more  symbol table entries to print.
	      Otherwise, it prints a RETURN/IF sequence and decrements  the
	      loop counter (KNT).

	  4.  Processes the next row (step 2) if the value of  KNT  is  not
	      zero.   If KNT is zero, this is the last row on this page and
	      STPRNT returns control to the caller.



     2.4.3  PRNT2 (Overlay 11)

     The routine PRNT2 sends the two 6-bit characters  in  the  AC  to  the
     listing  file.   It calls PRNT6 twice;  once to print the character in
     the left byte and once to print the character in the right byte.



     2.4.4  PRN (Overlay 13)

     The routine PRN prints a symbol name.  If the first word of  the  name
     (NAME1 of the symbol table work area) is negative, it removes the sign
     bit from NAME1 and prints a dollar sign($) followed by the  name.   If
     NAME1  is  positive,  it  prints  the  name  by  itself.  PRN performs
     successive calls to PRNT2 to do the actual printing.



     2.4.5  XPRINT (Overlay 13)

     The routine XPRINT prints  a  symbol's  binary  value  and  associated
     qualifying  information.   It  performs  according  to  the  following
     conditions:

	  1.  If the symbol is in the Loader  Symbol  Dictionary  (LSD)  so
	      that bit 9 of its flag word = l, control passes to one of the
	      four routines listed below.  This depends on  the  LSD  entry
	      type  specified in bits 10-ll of the flag word.  Entry types,
	      destinations and tasks are shown in Table 2-4.

	  2.  If the symbol is a macro name (.MACRO), XPRINT:

	      a.  Changes the value word (which has been moved  to  PRTVAL)
		  to  0.   It  does not change SYMVAL, because its contents
		  may be written back into the symbol table later.

	      b.  Prints an M before the symbol's value (0000).

	  3.  If the symbol is not one  of  the  types  covered  above,  it
	      prints a space before the symbol's value.




				     2-23
			  DESCRIPTIONS OF THE MODULES


				   Table 2-4
	 Loader Symbol Dictionary Entry Types, Destinations, and Tasks

     ----------------------------------------------------------------------
     |	Entry Type   |		     Destination and Task		  |
     |---------------|----------------------------------------------------|
     |		     |							  |
     |	     0	     | XENTRY and prints an E  (.ENTRY)  before  printing |
     |		     | the symbol's value.				  |
     |		     |							  |
     |	     1	     | XGLOB and prints a  G  (.GLOBAL)  before  printing |
     |		     | the symbol's value.				  |
     |		     |							  |
     |	     2	     | XEXT and prints an X (.EXTERNAL) or a Y  (.SECREF) |
     |		     | before  printing four asterisks (****) in place of |
     |		     | the symbol's value.				  |
     |		     |							  |
     |	     3	     | XZTE and prints a Z (.ZTERNAL) before  printing  a |
     |		     | zero  followed  by three asterisks (0***) in place |
     |		     | of the symbol's value.				  |
     ----------------------------------------------------------------------


	  4.  If the symbol is undefined (flag word is negative), it  calls
	      UNDF, which:

	      a.  Prints four asterisks followed by a left arrow (****<-- )
		  and a TAB in place of a value.

	      b.  Exits from the routine.

	  5.  If the symbol is defined, it calls OPRINT  (MAC30)  to  print
	      the  value  of  the  symbol  as  a  4-digit octal number with
	      leading zeros.

	  6.  If the symbol is a .SECT name, it prints two spaces  and  the
	      type  of  sect  (.ASECT,  .RSECT,  .FSECT, .DSECT, .ZSECT, or
	      .XSECT) to the right of the value.  It  obtains  the  program
	      section  type from bits 6-8 of the flag word, then exits from
	      the routine.

	  7.  If the symbol is not a .SECT name (flag bits 6-8 are  0),  it
	      branches  to NOTSCT, which performs a branch depending on the
	      symbol's type (bits 9-11 of the flag word).

	      a.  If the symbol is  a  .MACRO  name,  pseudo-macro,  MACREL
		  directive,  .EXTERNAL, .ZTERNAL, or absolute (implicit or
		  explicit .ASECT), it prints a TAB and exits.

	      b.  If the symbol is  a  .ENTRY  name,  a  .GLOBAL  name,  or
		  resides  in a relocatable program section, its value must
		  be displayed in relation to the beginning of the  program
		  section.   To show this, XPRINT prints a plus sign (+), a
		  space, and the name of  the  program  section  where  the

				     2-24
			  DESCRIPTIONS OF THE MODULES


		  symbol  resides.   Following  this, it prints a TAB, then
		  exits.



     2.4.6  PRNT6 (Overlay 13)

     The routine PRNT6 sends the 6-bit ASCII character in  the  right  (low
     order)  byte of the AC to the listing file.  It automatically converts
     MACREL's internal codes for dollar sign (33) and period (44) to  their
     6-bit  equivalents  (44  and 56 respectively).  It calls (QQ)LISTER to
     print the appropriate ASCII character.



     2.5  MACERR (Special Overlay)

     The MACERR module is the error message overlay.  It contains both  the
     routines  that  print  the  error messages and the error message text.
     This is a special overlay in the sense that it is  not  loaded  via  a
     call  to LOAD like the other MACREL overlays.  Instead, when a routine
     detects an error, it performs a  subroutine  jump  to  ERROR  (MAC24),
     which loads MACERR and passes control to ERRTN.


				    CAUTION

		    MACERR must always be exactly 23 blocks
		    long to allow ERROR to perform overlay
		    address computation.


     ERRTN uses the address of the error call to find and print the  actual
     error message text as follows:

	  1.  Obtains the address of the call (JMS), and  searches  for  an
	      entry  in  a table (ERLST) that contains the addresses of all
	      error calls.

	  2.  Finds the matching address in the table and  then  calculates
	      the  ordinal position of that entry from the beginning of the
	      table.

	  3.  Uses this value to  index  into  the  message  pointer  table
	      (MESLST)  and  obtain  a  pointer  that is the 12-bit virtual
	      address of the  desired  error  message  in  MACREL.SV.   The
	      pointer is the message's address that is assigned at assembly
	      time.  (Error message pointers have virtual addresses in  the
	      range 3400-7377.)

	  4.  Calculates the block number in MACREL.SV  where  the  message
	      resides  and  reads  this  block into a buffer that begins at
	      memory location 10400.  (Table  2-5  shows  the  relationship


				     2-25
			  DESCRIPTIONS OF THE MODULES


	      between  the block numbers in MACREL.SV and MACERR's assembly
	      time addresses.)

	  5.  Calculates exactly where an  error  message  resides  in  the
	      buffer (block).

	  6.  Prints the message on either  the  terminal,  the  BATCH  log
	      device,   or  in  the  listing,  using  the  output  routines
	      described in Table 2-6.

	  7.  Returns control to ERROR, when MACERR finishes to restore  to
	      memory the five blocks that it swapped out.  (It is important
	      that these blocks never contain code that calls ERROR.)

				   Table 2-5
		       Layout of MACERR Within MACREL.SV

		 --------------------------------------------		
		 | Relative |	       |   Assembly-time    |
		 |  Block   | Contents | Addresses (MACERR) |
		 |----------|----------|--------------------|
		 | 101-104  |	code   |   51000-52777	    |
		 | 105	    |  unused  |  (53000)	    |
		 | 106	    |    :     |   53400  ERRBLK+6  |
		 | 107	    |    :     |   54000	    |
		 | 110	    | message  |   54400	    |
		 | 111	    |   text   |   55000	    |
		 | 115	    |    :     |   55400	    |
		 | 113	    |    :     |   56000	    |
		 | 114	    |    :     |   56400	    |
		 | 115	    |    :     |   57000  ERRBLK+15 |
		 | 116-122  |	       |   60000-62377 *    |
		 --------------------------------------------		
	* These are the five blocks that are swapped to and from the swap
	area located at addresses 10400-12777 during run time.



     2.5.1  Error Typeout Routines

     MACERR contains the output routines listed in Table 2-6.


				   Table 2-6
			 MACERR Output Routine Summary

     ----------------------------------------------------------------------
     |	Name  |			     Task				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     | TYPERR | Types error message  on  error  log  (TTY  or  BATCH  log |
     |	      | file).							  |
     ----------------------------------------------------------------------
						 (continued on next page)

				     2-26
			  DESCRIPTIONS OF THE MODULES


			       Table 2-6 (Cont.)
			 MACERR Output Routine Summary

     ----------------------------------------------------------------------
     |	Name  |			     Task				  |
     |--------|-----------------------------------------------------------|
     | PRCHR  | Prints  single  characters  on  a  device  specified   by |
     |	      | OUTDEY.   (The  AC  will be non-zero when PCHR returns to |
     |	      | the caller.)						  |
     |	      |								  |
     | PRNAM  | Prints a  6-character  name  on  a  device  specified  by |
     |	      | OUTDEY.  (The AC will be non-zero when PRNSM  returns  to |
     |	      | the caller.)						  |
     |	      |								  |
     | PR6A   | Prints a 6-bit ASCII character on a device  specified  by |
     |	      | OUTDEY, ignoring NULs.					  |
     |	      |								  |
     | SETNAM | Sets up name to be printed by PRNAM;   followed  by  CDF, |
     |	      | then PTR.						  |
     |	      |								  |
     | PR     | Prints a character on the error log device if  CTRL/O  is |
     |	      | not  in  effect.  Also checks for CTRL/O, CTRL/C, CTRL/S, |
     |	      | and the E, F, and L options.				  |
     |	      |								  |
     | TPUT   | Types a character unconditionally on the error log device.|
     |	      |								  |
     | TP     | Types a character unconditionally on the terminal.	  |
     |	      |								  |
     | PR2    | Prints two 6-bit ASCII characters using PR.		  |
     |	      |								  |
     | PRO    | Prints one 6-bit ASCII character using PR.		  |
     |	      |								  |
     | PR12   | Prints one 12-bit number as 4 octal digits using PR.	  |
     |	      |								  |
     | STNAM  | Sets up a symbol table name for printing, and obtains the |
     |	      | value of the symbol in VAL.				  |
     |	      |								  |
     | CHKKBD | Checks to see if CTRL/C, CTRL/S, CTRL/O, E, F, or  L  was |
     |	      | typed on the keyboard.					  |
     |	      |								  |
     | OUTDEY | Contains either PR or LPUT,  as  set  up  by  TYPERR  and |
     |	      | PRNERR.							  |
     |	      |								  |
     | CRLFF  | Prints carriage return/linefeed on OUTDEY.		  |
     |	      |								  |
     | TYPE   | Prints a 6-bit ASCII character (carriage return/line feed |
     |	      | if NUL character) on a device specified by OUTDEY.	  |
     ----------------------------------------------------------------------



     2.5.2  Creating New Error Messages

     The following rules describe how to create new error messages.

				     2-27
			  DESCRIPTIONS OF THE MODULES


	  1.  The calling routine must:

	      a.  Make sure that the data field is set to  the  data  field
		  here the routine resides.

	      b.  Perform a call to ERROR as follows:

		  ERnnn, JMS QQERROR

	      where:

	      ERnnn  is  a  defined  as  a  global  symbol  in  the  global
	      definition file MGLOB.MA

	  2.  The error address table, ERLST, must contain an entry that is
	      the  negated  address  value  of  the location of the call to
	      ERROR.  A -1 ends this table.  The form of the entry is:

		   .EXTERNAL ERnnn -ERnnn

	  3.  The message pointer table, MESLST, must contain an entry that
	      is  in  the same relative position as its corresponding entry
	      in ERLST.  (The pointers are grouped by module.)

	  4.  The error message table must contain a message in the form:

		   adr pass TEXT /xx msg/

	      where:

		   adr	    is the address of the fixup routine (This is  a
			    routine   that   can   be   called  to  perform
			    preprocessing  before  the  error  message   is
			    printed.   If  this  entry  is 0, no routine is
			    called.)

		   pass	    is the number of the physical  pass  where  the
			    error was detected

		   xx	    is the two-character error message code

		   msg	    is the text of the error message

     The pass number represents the physical (not logical) pass  number  on
     which  this error message should be given.  For example if there is no
     binary requested, then the listing pass is physical pass 2 even though
     it  is logical pass 3.  No message is given if this is the wrong pass.
     The assumption is that the message  has  already  been  printed  on  a
     previous pass.  This avoids message duplication.

     For errors that are pass independent, such as I/O errors, MACREL  uses
     the  pass  number code 4000.  These messages are printed regardless of
     which pass is in effect.


				     2-28
			  DESCRIPTIONS OF THE MODULES


     Two special codes are permitted within the text of the error message:

	  #   Print the symbol name that is in NAME1 through NAME3  of  the
	      symbol  table  work  area  (MAC24) at this point in the error
	      message.

	  ?   Print the character enclosed in quotes residing  in  CHAR  at
	      this point in the error message.



     2.5.3  Number of Errors Detected

     In order to print the number of errors  detected,  FIN0  simulates  an
     error at the end of the assembly using ER230 (FIN0).  The ER1 (MACERR)
     routine prints the ERRORS  DETECTED  message  if  necessary  and  then
     returns to the address immediately following the ER230 label.



     2.6  MACEXP

     The module MACEXP contains the memory-resident routines  that  perform
     expression parsing.  It consists of the main routine EXPR and a number
     of subordinate routines.  MACEXP loads its extension overlay,  EXPOVR,
     only as needed.



     2.6.1  EXPR

     EXPR is the controlling routine for expression parsing.  Routines call
     EXPR  to  parse  an expression beginning with the current character in
     the input stream.  The call to EXPR is:

	  JMS I (QQEXPR

     Control returns to the caller at the address stored in EXPR  with  the
     absolute  (12-bit)  part of the expression in the accumulator (AC) and
     the relative part of the expression in EXPREL (15-bit pointer).

     EXPR operates recursively.  Before it calls itself, it saves the local
     variables  listed in Table 2-7 on the expression stack (EXPSTK).  When
     it returns from the (recursive) call, it removes these variables  from
     the stack and restores EXPR to its previous operational state.

     EXPR performs the following tasks.

	  1.  Sets the variables PRVOPR,  EXPABS,  EXPREL,  and  EXPCOD  to
	      zero.   This  specifies  that no previous binary operator has
	      been found and that the initial value of the expression is 0.

	  2.  Calls TERM to obtain and evaluate a term of the expression.


				     2-29
			  DESCRIPTIONS OF THE MODULES


				   Table 2-7
		 Local Variables Saved on the Expression Stack

     ----------------------------------------------------------------------
     |	 Name	|			Use				  |
     |----------|---------------------------------------------------------|
     |		|							  |
     |  EXPABS  | Absolute part of total expression computed so far	  |
     |		|							  |
     |  EXPCOD  | Relocation type:					  |
     |		|		   -1 = Value of expression is top entry  |
     |		|			on LINK's stack.		  |
     |		|		    0 = Simple relocation; add absolute	  |
     |		|			part to relative part		  |
     |		|		    1 = .FSECT relocation		  |
     |		|		    2 = CDF relocation; add field of	  |
     |		|			relative part, multiplied by 10	  |
     |		|			(octal) to absolute part	  |
     |		|							  |
     |  EXPR	| Return address from EXPR				  |
     |		|							  |
     |  EXPREL  | Relative part of result of total expression so far	  |
     |		| computed						  |
     |		|							  |
     |  TERM	| Return address from TERM				  |
     |		|							  |
     |  UNARYM  | Number of minuses seen on term to be combined with	  |
     |		| expression result					  |
     |		|							  |
     |  PRVOPR	| Previous operator;  used to combine new value with old  |
     |		| result						  |
     ----------------------------------------------------------------------


	  3.  (if it cannot perform the requested binary operation)

	      a.  Calls HARD to set up loader codes that  request  LINK  to
		  perform the operation.

	      b.  Obtains the next operator and stores its code  in  PRVOPR
		  (see Table 2-7).

	      c.  Calls TERM again (step 2 above).

	  4.  (if it can perform the  requested  binary  operation)  Passes
	      control  to  the  routine  specified by the code in PRVOPR to
	      process the previous operator (see Table  2-8).   On  return,
	      the results reside in EXPABS, EXPREL, and EXPCOD.







				     2-30
			  DESCRIPTIONS OF THE MODULES


				   Table 2-8
		     EXPR Previous Operator Dispatch Table

     ----------------------------------------------------------------------
     | Code |	 Operator    | Processing Routine |	     Use	  |
     |------|----------------|--------------------|-----------------------|
     |	0   | NUL	     | NOPREV		  | No previous operator  |
     |	1   | +		     | ADD		  | Addition		  |
     |	2   | -		     | SUB		  | Subtraction		  |
     |	3   | ^		     | MUL		  | Multiplication	  |
     |	4   | %		     | DIV		  | Division		  |
     |	5   | <space> or TAB | OR		  | Logical inclusive OR  |
     |	6   | &		     | ANDY		  | Logical AND		  |
     |	7   | !		     | SHIFT		  | 6-bit left shift	  |
     |	10  | !		     | OR		  | Logical inclusive OR  |
     ----------------------------------------------------------------------



     2.6.2  TERM

     The routine TERM parses and evaluates a term from  the  current  input
     stream.  The calling sequence is:

	  JMS	  TERM
		  address if term is empty
		  address for normal return

     It  scans  all  characters  and  passes  control  to  the  appropriate
     processing  routine  listed in Table 2-9.  It skips over spaces and if
     the term is empty, returns control to the caller at the  first  return
     address.   Control  normally  returns  to  TRM's  caller at the second
     return address.


				   Table 2-9
			 TERM Character Dispatch Table

     ----------------------------------------------------------------------
     |	 Character   |Processing|		  Function		  |
     |		     | Routine  |					  |
     |---------------|----------|-----------------------------------------|
     |		     |		|					  |
     | A - Z, a - z  |	SYMM	| Parses a symbol period (.), performs  a |
     | and comma (,) |		| symbol  table  lookup,  and  exits from |
     |		     |		| TERM.					  |
     |		     |		|					  |
     | 0 - 9	     |  NUMBR	| Parses a number and exits from TERM.	  |
     |		     |		|					  |
     | -	     |  UNOPM	| Increments the  minus  sign  count  and |
     |		     |		| reiterates TERM.			  |
     ----------------------------------------------------------------------
						 (continued on next page)


				     2-31
			  DESCRIPTIONS OF THE MODULES


			       Table 2-9 (cont.)
			 TERM Character Dispatch Table

     ----------------------------------------------------------------------
     |	 Character   |Processing|		  Function		  |
     |		     | Routine  |					  |
     |---------------|----------|-----------------------------------------|
     | (	     |  PENP	| Parses   a   current    page    literal |
     |		     |		| (including   the   right  parenthesis), |
     |		     |		| performs a  symbol  table  lookup,  and |
     |		     |		| exits from TERM.			  |
     |		     |		|					  |
     | [	     |  OPENB	| Parses a page zero  literal  (including |
     |		     |		| the  right  square bracket), performs a |
     |		     |		| symbol table  lookup,  and  exits  from |
     |		     |		| TERM.					  |
     |		     |		|					  |
     | "	     |  DBLQ	| Parses an expression of the form:   'A, |
     |		     |		| where  A  is  a  single  character.  It |
     |		     |		| inserts the 8-bit ASCII  code  for  the |
     |		     |		| character  in TRMABS if bit 4 of ENABWD |
     |		     |		| is set to a 1, then exits from TERM.	  |
     |		     |		|					  |
     | '	     |  SNGL