HLASM Language Reference
HLASM Language Reference HLASM Language Reference
Addressing External Symbol Dictionary Entries For each section, class, part, entry, external symbol, and dummy external control section, the assembler keeps a record of the following external symbol dictionary (ESD) information: Symbolic name, if one is specified Type code Individual identification number (ESDID) Starting address Length Owning ESDID, if any Symbol attributes Alias, if one is specified Figure 20 lists the assembler instructions that define control sections and dummy control sections, classes and parts, or identify entry and external symbols, and tells their associated type codes. You can define up to 65535 individual control sections and external symbols in a source module if the NOGOFF option is specified, or up to 999999 external symbols if the GOFF option is specified. Figure 20. Defining External Symbols Name Entry Instruction Coding Entered into External Symbol Dictionary If present START, CSECT, or RSECT NOGOFF option SD GOFF option SD, ED, LD If omitted START, CSECT, or RSECT PC SD Instructiondependent Any instruction that initiates the unnamed section PC SD Optional COM CM CM Optional DSECT None None Mandatory DXD or external DSECT XD XD Mandatory CATTR Not applicable ED Mandatory CATTR PART(name) Not applicable PD Not applicable ENTRY LD LD Not applicable EXTRN ER ER Not applicable DC (V-type address constant) ER ER Not applicable WXTRN WX WX Refer to Appendix C Object Deck Output in the HLASM Programmer's Guide, SC26-4941 for details about the ESD entries produced when you specify the NOGOFF assembler option. Refer to z/OS MVS Program Management: Advanced Facilities, SA22-7644 for details about the ESD entries produced when you specify the GOFF assembler option. 72 HLASM V1R5 Language Reference
Addressing | Summary of Source and Object Program Structures | The differences between the load module model and the program object model, | and their interactions with assembler language instructions, are summarized in the | following table: | Property “Load Module” Model “Program Object” Model | Form of object program One-dimensional module Two-dimensional module | Smallest indivisible independently Control section Element and part | relocatable component | Residence Mode Only one One per class | Addressing Mode Only one One per entry point | Compatibility Can be converted to program Can be converted to load module | object with limitations | Assembler Option NOGOFF or GOFF GOFF only | Assembler statements CSECT, RSECT, START CSECT, RSECT, START, CATTR, | XATTR | Assignable loadable-program RMODE RMODE, alignment, load type | attributes | External symbol types SD/CM, LD, ER/WX, PR SD, ED, LD, ER/WX, PR, PD | External symbol maximum length 8 characters 256 characters | External symbol scope Module (WX), Library (ER) Section, Module, Library, | Import/Export | External symbol attributes AMode, RMode AMode, RMode, scope, PSect name, | linkage type, reference type, | extended attributes | Object module record types ESD, TXT, RLD, END, SYM HDR, ESD, TXT, RLD, END, LEN | Address constant types A, V, Q, CXD A, V, Q, J, R, CXD | Binding attributes Catenate (SD), Catenate (non-Merge classes), | Merge-like (CM,PR) Merge classes (Parts, | Pseudo-Registers) | Text types Byte stream Byte stream, records (structured and | unstructured) | Maximum contiguous text length 16MB 1GB | Figure 21. Object Program Structure Comparison Chapter 3. Program Structures and Addressing 73
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Addressing<br />
External Symbol Dictionary Entries<br />
For each section, class, part, entry, external symbol, and dummy external control<br />
section, the assembler keeps a record of the following external symbol dictionary<br />
(ESD) information:<br />
Symbolic name, if one is specified<br />
Type code<br />
Individual identification number (ESDID)<br />
Starting address<br />
Length<br />
Owning ESDID, if any<br />
Symbol attributes<br />
Alias, if one is specified<br />
Figure 20 lists the assembler instructions that define control sections and dummy<br />
control sections, classes and parts, or identify entry and external symbols, and tells<br />
their associated type codes. You can define up to 65535 individual control sections<br />
and external symbols in a source module if the NOGOFF option is specified, or up<br />
to 999999 external symbols if the GOFF option is specified.<br />
Figure 20. Defining External Symbols<br />
Name Entry Instruction Coding Entered into External Symbol<br />
Dictionary<br />
If present<br />
START, CSECT, or RSECT<br />
NOGOFF option<br />
SD<br />
GOFF option<br />
SD, ED, LD<br />
If omitted<br />
START, CSECT, or RSECT<br />
PC<br />
SD<br />
Instructiondependent<br />
Any instruction that initiates<br />
the unnamed section<br />
PC<br />
SD<br />
Optional<br />
COM<br />
CM<br />
CM<br />
Optional<br />
DSECT<br />
None<br />
None<br />
Mandatory<br />
DXD or external DSECT<br />
XD<br />
XD<br />
Mandatory<br />
CATTR<br />
Not applicable<br />
ED<br />
Mandatory<br />
CATTR PART(name)<br />
Not applicable<br />
PD<br />
Not applicable<br />
ENTRY<br />
LD<br />
LD<br />
Not applicable<br />
EXTRN<br />
ER<br />
ER<br />
Not applicable<br />
DC (V-type address constant)<br />
ER<br />
ER<br />
Not applicable<br />
WXTRN<br />
WX<br />
WX<br />
Refer to Appendix C Object Deck Output in the <strong>HLASM</strong> Programmer's Guide,<br />
SC26-4941 for details about the ESD entries produced when you specify the<br />
NOGOFF assembler option.<br />
Refer to z/OS MVS Program Management: Advanced Facilities,<br />
SA22-7644 for details about the ESD entries produced when you specify the GOFF<br />
assembler option.<br />
72 <strong>HLASM</strong> V1R5 <strong>Language</strong> <strong>Reference</strong>
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