Program Logic Manual - All about the IBM 1130 Computing System

SECTION 10. ASSEMBLER PROGRAMFLOWCHARTSGeneral: ASMO1Phase 0: ASMO2Phase 1: ASMO3Phase 1A: ASMO4Phase 2: ASMO5Phase 2A: ASMO6Phase 3: ASMO7Phase 4: ASMO8Phase 5: ASMO9Phase 6: ASM10Phase 7: ASM11Phase 7A: ASM12Phase 8: ASM13Phase 8A: ASM14Phase 9: ASM15-ASM17Phase 10: ASM18Phase 10A: ASM19Phase 11: ASM20Phase 12: ASM21ERMSG: ASM22@ARCV ASM23@APCV:Phase 13:ASM24ASM25 -ASM26The Assembler Program is designed to translate thestatements of a source program written in 1130Assembler Language into a format that may bedumped and/or stored by DUP or executed directlyfrom Working Storage.Basically, the functions of the Assembler are:1. Convert the mnemonic to machine language(except for Assembler control records).2. Assign addresses to statement labels.3. Insert the format and index register bits intothe instruction, if applicable.4. Convert the instruction operands to addressesor data.INTRODUCTIONThe Assembler Program is structurally divided intotwo parts, the resident portion and the overlay portion.The resident portion consists of the AssemblerCommunications Area (ASCOM), part of phase 0,phase 9, and the phase 9 Communications Area(PHSCO). All of the other phases are called intocore storage as overlays.The Assembler Program is functionally dividedinto two parts, pass 1 and pass 2. The source programis read and processed, one statement at atime, during each of the two passes. During pass 1,the source program is read into core storage fromthe principal I/0 device. Unless the user specifiesby control record that two-pass mode is in effect,the source program is stored on the disk, fromwhich it is reentered for pass 2 processing. If twopassmode is specified or required, the source programis reentered via the principal I/O device forpass 2 processing. (If a list deck or paper tapeobject program is desired, the assembly must bemade in two-pass mode.)PROGRAM OPERATIONWhen the Monitor Control Record Analyzer detectsan ASM monitor control record, it reads the firstsector of the Assembler Program (phase 0) intocore storage and transfers control to it.Phase 0 reads into core storage all the subroutinesrequired during assembly processing for I/O,and phase 9. The word counts and sector addressesof all the buffers and major overlay phases are initializedin ASCOM and in phase 9, and the boundaryconditions are set for the Symbol Table. Phase 1is then fetched and control is passed to it.Phase 1 reads and analyzes control records, settingthe appropriate switches in ASCOM for the optionsspecified. Upon detection of the first non-controlrecord, phase 1A is fetched and given control.Phase 1A initializes the core addresses for thebuffers, then fetches and transfers control to phase2 to start statement processing.Statement processing is performed by an op codesearch in phase 9 arid a transfer through a branchtable (that precedes every major overlay) to theoverlay phase currently in core storage. If the requiredoverlay phase is in core storage, executionof the phase proceeds. If it is not in core storage,the branch table causes a return to phase 9 to fetchthe required overlay phase. The op code search isperformed again and control is passed to the overlaySection 10. Assembler Program 65