HLASM Language Reference

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Lookahead MACRO &NAME MOVE &TO,&FROM Statement 1 &NAME ST 2,SAVEAREA Statement 2 L 2,&FROM ST 2,&TO L 2,SAVEAREA MEND ------------------------------------------------------------------ .SYM MOVE FIELDA,FIELDB Statement 3 ------------------------------------------------------------------ + ST 2,SAVEAREA Statement 4 + L 2,FIELDB + ST 2,FIELDA + L 2,SAVEAREA The symbolic parameter &NAME is used in the name field of the prototype statement (Statement 1) and the first model statement (Statement 2). In the macro instruction (Statement 3), a sequence symbol (.SYM) corresponds to the symbolic parameter &NAME. &NAME is not replaced by .SYM and, therefore, the generated statement (Statement 4) does not contain an entry in the name field. Lookahead Symbol attributes are established in either definition mode or lookahead mode. Definition mode occurs whenever a previously undefined symbol is encountered in the name field of a statement, or in the operand field of an EXTRN or WXTRN statement during open code processing. Symbols within a macro definition are defined when the macro is expanded. Lookahead mode is entered: When the assembler processes a conditional assembly instruction and encounters an attribute reference (other than D' and O') to an ordinary symbol that is not yet defined. When the assembler encounters a forward AGO or AIF branch in open code to a sequence symbol that is not yet defined. Lookahead is a sequential, statement-by-statement, forward scan over the source text. If the attribute reference is made in a macro, forward scan begins with the first source statement following the outermost macro instruction. During lookahead the assembler: Bypasses macro definition and generation Does not generate object text Does not perform open-code variable substitution Ignores AIF and AGO branch instructions Establishes interim data attributes for undefined symbols it encounters in operand fields of instructions. The data attributes are replaced when a symbol is subsequently encountered in definition mode. Lookahead mode ends when the desired symbol or sequence symbol is found, or when the END statement or end of file is reached. All statements read by 340 HLASM V1R5 Language Reference
Lookahead lookahead are saved on an internal file, and are fully processed when the lookahead scan ends. If a COPY instruction is encountered during lookahead, it is fully processed at that time, the assembler copies the statements from the library, scans them, and saves them on the lookahead file. When lookahead mode has ended any COPY instructions saved to the lookahead file are ignored, as the statements from the copy member have already been read and saved to the lookahead file. If a variable symbol is used for the member name of a COPY that is expanded during lookahead, the value of the variable symbol at the time the COPY is expanded is used. For purposes of attribute definition, a symbol is considered partially defined if it depends in any way upon a symbol not yet defined. For example, if the symbol is defined by a forward EQU that is not yet resolved, that symbol is assigned a type attribute of U. In this case, it is quite possible that, by the end of the assembly, the type attribute has changed to some other value. Generating END statements: Because no variable symbol substitution is carried out during lookahead, you should consider the following effects of using macro, AINSERT or open code substitution to generate END statements that separate source modules assembled in one job step (BATCH assembler option). If a symbol is undefined within a module, lookahead might read statements past the point where the END statement is to be generated. Lookahead stops when: 1. It finds the symbol 2. It finds an END statement 3. It reaches the end of the source input data set In the first two cases, the assembler begins the next module at the statement after lookahead stopped, which could be after the point where you wanted to generate the END statement. Lookahead Restrictions The assembler analyzes the statements it processes during lookahead, only to establish attributes of symbols in their name fields. Variable symbols are not replaced. Modifier expressions are evaluated only if all symbols involved were defined prior to lookahead. Possible multiple or inconsistent definition of the same symbol is not diagnosed during lookahead because conditional assembly may eliminate one (or more) of the definitions. Lookahead does not check undefined operation codes against library macro names. If the name field contains an ordinary symbol and the operation code cannot be matched with one in the current operation code table, then the ordinary symbol is assigned the type attribute of M. If the operation code contains special characters or is a variable symbol, a type attribute of U is assumed. This may be wrong if the undefined operation code is later substituted with a known operation code or is later defined by OPSYN. OPSYN statements are not processed; thus, labels are treated in accordance with the operation code definitions in effect at the time of entry to lookahead. Chapter 9. How to Write Conditional Assembly Instructions 341
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High Level Assembler for MVS & VM &
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Note! Before using this information
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Contents Source Module . . . . . .
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Contents Ordinary USING Instruction
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Contents Sublists in Operands . . .
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About this Manual This manual descr
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IBM High Level Assembler for MVS &
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| The Internet. You can access IBM
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▌C▐ The item referred to by ▌
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Miscellany The ASCII translation t
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Part 1. Assembler Language—Struct
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Language Compatibility Language Com
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Assembler Program Assembler Program
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Relationship of Assembler to Operat
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Coding Made Easier Linkage between
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Character Set Compatibility with Ea
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Assembler Language Coding Conventio
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Assembler Language Structure Condit
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Assembler Language Structure Machin
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Assembler Language Structure Condit
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Terms, Literals, and Expressions Te
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Terms, Literals, and Expressions -
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Terms, Literals, and Expressions As
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Terms, Literals, and Expressions Se
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Terms, Literals, and Expressions Fo
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Terms, Literals, and Expressions I
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Terms, Literals, and Expressions Th
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Terms, Literals, and Expressions 1.
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Terms, Literals, and Expressions
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Terms, Literals, and Expressions
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Terms, Literals, and Expressions Th
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| Chapter 3. Program Structures and
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Source Module A source module is co
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The CSECT instruction can be used a
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| in linker control statements for
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This is not only convenient, but it
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| SECT_A CSECT , Define section SEC
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| For executable sections, the loca
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Addressing | The System/390® and z
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Addressing | Parts must always be r
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Addressing Literal Pools ALPHA LR 3
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Addressing If the symbol is the nam
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Addressing External Symbol Dictiona
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Addressing 74 HLASM V1R5 Language R
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Part 2. Machine and Assembler Instr
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General Instructions Chapter 4. Mac
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Input/Output Operations For further
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Branching with Extended Mnemonic Co
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Symbolic Operation Codes variations
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Operand Entries Registers You can s
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Operand Entries “Program Structur
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Operand Entries Format │ Coded or
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Examples of Coded Machine Instructi
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Chapter 5. Assembler Instruction St
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*PROCESS Statement *PROCESS Stateme
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ACONTROL Instruction ►►──
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ACONTROL Instruction FLAG(PAGE0) in
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AINSERT Instruction character_strin
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AMODE Instruction alias_string is t
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CATTR Instruction Figure 25. AMODE/
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CATTR Instruction | statements for
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CCW1 Instruction data_count is an a
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CEJECT Instruction If symbol is an
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CNOP Instruction Figure 29 (Page 2
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COPY Instruction In the following e
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CSECT Instruction symbol in the nam
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DC Instruction ROUTINE B GAMMA DXD
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DC Instruction duplication_factor c
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DC Instruction Figure 33 (Page 2 of
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DC Instruction With EBCDIC spaces
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DC Instruction Further information
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DC Instruction | Symbols used in su
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DC Instruction The length attribute
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DC Instruction Notes: 1. Don't conf
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DC Instruction—Character Constant
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DC Instruction—Character Constant
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DC Instruction—Graphic Constant r
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DC Instruction—Fixed-Point Consta
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DC Instruction—Fixed-Point Consta
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DC Instruction—Decimal Constants
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DC Instruction—Address Constants
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DC Instruction—Address Constants
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DC Instruction—Offset Constant re
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DC Instruction—Length Constant Le
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DC Instruction—Hexadecimal Floati
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DC Instruction—Binary Floating-Po
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DC Instruction—Binary Floating-Po
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DROP Instruction DROP Instruction T
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DS Instruction USING DSECTA,14 ALBL
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DS Instruction The size of a storag
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DSECT Instruction DSECT Instruction
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DXD Instruction ASEMBLY2 CSECT USIN
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END Instruction change but no addit
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EQU Instruction EQU Instruction The
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EQU Instruction 5. The length attri
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EXITCTL Instruction sequence_symbol
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ISEQ Instruction must be greater th
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LOCTR Instruction A CSECT , See not
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LTORG Instruction If symbol is an o
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MNOTE Instruction When two literals
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OPSYN Instruction ,ERROR, SEV 1 An
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ORG Instruction AFTER is defined in
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ORG Instruction If you specify mult
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POP Instruction POP Instruction The
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PRINT Instruction Note: If the next
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Process Statement Process Statement
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REPRO Instruction NOPRINT instructs
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RSECT Instruction 4. AMODE or RMODE
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START Instruction START Instruction
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TITLE Instruction The name value is
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USING Instruction Only the characte
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USING Instruction Base Registers fo
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USING Instruction If register 0 is
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USING Instruction A variable symbo
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USING Instruction In this MVC instr
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USING Instruction Range of a Depend
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XATTR Instruction external_symbol i
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XATTR Instruction SCOPE ►►─
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XATTR Instruction 234 HLASM V1R5 La
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Part 3. Macro Language &SYSDATC Sys
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Introduction to Macro Language Chap
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Introduction to Macro Language The
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Introduction to Macro Language Macr
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MACRO and MEND Statements The assem
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Prototype Statement Macros that are
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Model Statements generated from tha
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Model Statements ▌5▐ ▌6▐
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Model Statements Notes: 1. You can
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Positional Parameters Symbolic para
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Processing Statements Processing St
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AREAD Instruction Assign Local Time
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COPY Instruction sequence_symbol is
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System Variable Symbols System Vari
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&SYSADATA_MEMBER System Variable Sy
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&SYSCLOCK System Variable Symbol &S
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&SYSECT System Variable Symbol depe
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&SYSIN_MEMBER System Variable Symbo
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&SYSJOB System Variable Symbol &SYS
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&SYSLIN_DSN System Variable Symbol
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&SYSLIST System Variable Symbol The
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&SYSLOC System Variable Symbol To
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&SYSM_SEV System Variable Symbol &S
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&SYSNDX System Variable Symbol The
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&SYSOPT_DBCS System Variable Symbol
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&SYSPARM System Variable Symbol Not
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&SYSPRINT_MEMBER System Variable Sy
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Page 314 and 315: &SYSTERM_DSN System Variable Symbol
Page 316 and 317: &SYSTIME System Variable Symbol Not
Page 318 and 319: Macro Instruction Format sequence_s
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Page 322 and 323: Macro Instruction Format When you n
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Page 326 and 327: Sublists in Operands &SYSLIST( n,m)
Page 328 and 329: Values in Operands Notes: 1. Spaces
Page 330 and 331: Values in Operands Parentheses In m
Page 332 and 333: Inner and Outer Macro Instructions
Page 334 and 335: Levels of Macro Call Nesting When t
Page 336 and 337: Levels of Macro Call Nesting System
Page 338 and 339: How to Write Conditional Assembly I
Page 340 and 341: SET Symbols SET Symbol Specificatio
Page 342 and 343: SET Symbols Figure 86 (Page 3 of 3)
Page 344 and 345: Data Attributes this example indica
Page 346 and 347: Data Attributes variable_symbol is
Page 348 and 349: Data Attributes The value of an att
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Page 354 and 355: Data Attributes The scale attribute
Page 356 and 357: Data Attributes Number Attribute (N
Page 358 and 359: Data Attributes The operation code
Page 362 and 363: Open Code Sequence Symbols The cond
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Page 366 and 367: LCLA, LCLB, and LCLC Instructions s
Page 368 and 369: SETA Instruction expression is an a
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Page 382 and 383: SETB Instruction Any expression tha
Page 384 and 385: SETB Instruction ┌─────
Page 386 and 387: SETB Instruction | ISDEC | Format:
Page 388 and 389: SETB Instruction The two comparands
Page 390 and 391: SETC Instruction Notes: 1. The asse
Page 392 and 393: Figure 103. Substring Notation in C
Page 394 and 395: Loc Object Code Addr1 Addr2 Stmt So
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Page 400 and 401: SIGNED Format: Logical-expression,
Page 402 and 403: | X2D('') has value '+' | X2D('91')
Page 404 and 405: Concatenation of strings containing
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Page 408 and 409: SETAF Instruction Alternative State
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Branching Branching You can control
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AGO Instruction The extended AIF in
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ACTR Instruction AGOB—Synonym of
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ANOP Instruction statement processe
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MHELP Instruction MHELP B'10000000'
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400 HLASM V1R5 Language Reference
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Assembler Instructions and Statemen
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Summary of Constants Figure 113. Su
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Macro and Conditional Assembly Lang
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Standard Character Set Code Table H
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Standard Character Set Code Table H
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Trademarks AIX BookMaster CICS DFSM
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Bibliography SMP/E Reference, SC28-
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Index A2C (SETC built-in function)
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Index B B-type binary constant 141
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Index conditional assembly instruct
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Index elements of conditional assem
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Index instructions (continued) asse
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Index machine instruction statement
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Index operands (continued) compatib
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Index relative addressing 67 reloca
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Index sublists compatibility with A
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Index variable symbols (continued)
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Readers' Comments High Level Assemb
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IBM® Program Number: 5696-234 Prin
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