This glossary defines terms that are used in the High Level Assembler publications. Some of these terms might not be used in this publication.

If you do not understand the meaning of a data processing term used in any of the definitions below, refer to Vocabulary for Data Processing, Telecommunications, and Office Systems, GC20-1699.

IBM is grateful to the American National Standards Institute (ANSI) for permission to reprint its definitions from the American National Standard Vocabulary for Information Processing, which was prepared by Subcommittee X3K5 on Terminology and Glossary of American National Standards Committee X3. ANSI definitions are preceded by an asterisk (*).

absolute expression

An expression is absolute if its value does not change upon program relocation.

absolute value

Is the value of a term when that value does not change upon program relocation.

ADATA

(See associated data.) An assembler option causing it to produce associated data.

addressing mode (24-bit)

A System/370 addressing mode (AMODE) of the extended architecture that allows a program to run using 24-bit addresses. When operating in 24-bit mode, S/370 addressing architecture is applied. Other facilities of the extended architecture (see below) can be used. Only the low-order 24 bits of an address are used; the high-order bits are ignored.

addressing mode (31-bit)

An extended architecture addressing mode (AMODE) that allows a program to run using 31-bit addresses, other facilities of the extended architecture, or both. When operating in 31-bit mode, extended architecture addressing is applied, and all but the high-order bit of an address are used to address storage.

assemble

To prepare a machine language program from a symbolic language program by substituting machine operation codes for symbolic operation codes and absolute or relocatable addresses for symbolic addresses.

*assembler

A computer program that assembles.

assembler instruction

An assembler language source statement that causes the assembler to do a specific operation. Assembler instructions are not translated into machine instructions.

assembler language

A source language that includes symbolic machine language statements in which there is a one-to-one correspondence with the instruction formats and data formats of the computer. The assembler language also contains statements that represent assembler instructions and macro instructions.

associated data

Additional information produced by the assembler containing detailed machine-readable information about the assembly.

automatic library call

The process by which the linkage editor or binder resolves external references by including additional members from the automatic call library.

bimodal program execution

A function of the extended architecture (see "addressing mode (31-bit)") that allows a program to run in 24-bit or 31-bit addressing mode. The addressing mode is under program control.

binder

The component of DFSMS/MVS which is responsible for linking and editing programs, to create either record format load modules or program objects. The z/OS binder is a functional replacement for the z/OS linkage editor.

bracketed DBCS

DBCS characters enclosed with a shift-out (SO) character and a shift-in character (SI) to identify them from SBCS, and containing no SBCS characters except SO and SI.

class

A cross-section of program object data with uniform format, content, function, and behavioral attributes.

code page

An assignment of graphic characters and control function meanings to all code points.

code point

A 1-byte code representing one of 256 potential characters.

COMMON

A control section having a length attribute but no machine language text, for which space is reserved in the executable program.

conditional assembly language

A programming language that the assembler processes during conditional assembly. The conditional assembly language can be used to perform general arithmetic and logical computations, generate machine and assembler instructions from model statements, and provide variable symbols to represent data and vary the content of model statements during generation. It can be used in macro definitions, and in open code.

CONTROL PROGRAM.

A program that is designed to schedule and supervise the performance of data processing work by a computing system; an operating system.

control section (CSECT)

That part of a program specified by the programmer to be a relocatable unit, all elements of which are to be loaded into adjoining main storage locations.

data attributes

Values assigned by the assembler which describe the characteristics of ordinary symbols and variable symbols that represent data.

*diagnostic

Pertaining to the detection and isolation of a malfunction or mistake.

double-byte character set (DBCS)

DBCS is a means of providing support for Ideographic Languages which contain too many symbols to be represented by a single-byte character set such as EBCDIC. A valid double-byte character is defined as either DBCS space (X'4040'), or a pair of bytes, each of which must be in the range X'41' to X'FE', inclusive.

double-byte data

Double-byte character strings are commonly referred to as double-byte data.

dummy control section (DSECT)

A control section that an assembler can use to map an area of storage without producing any object code or data for that area. Synonymous with dummy section.

edited text

Source statements modified by the assembler for internal use. The initial processing of the assembler is referred to as editing.

element

The unit of program object data uniquely identified by a section name and a class name.

enterprise systems architecture

A hardware architecture for the IBM 3090 processor. A major characteristic is 31-bit addressing. See also "addressing mode (31-bit)".

*entry point

A location in a module to which control can be passed from another module or from the control program.

extended architecture

A hardware architecture for systems beginning with the IBM 3081. A major characteristic is 31-bit addressing. See also "addressing mode (31-bit)".

external symbol dictionary (ESD)

Control information associated with an object or load module which identifies the external symbols in the module.

global dictionary

An internal table used by the assembler during macro generation to contain the current values of all unique global SETA, SETB, and SETC variables from all text segments.

global vector table

A table of pointers in the skeleton dictionary of each text segment showing where the global variables are located in the global dictionary.

GOFF

Generalized Object File Format.

hierarchical file system

In z/OS UNIX System Services, a Hierarchical File System (HFS) is a collection of files organized in a hierarchy, as in a UNIX system. All files are members of a directory, and each directory is in turn a member of another directory at a higher level in the hierarchy. The highest level of the hierarchy is the root directory. z/OS views an entire file hierarchy as a collection of hierarchical file system data sets (HFS data sets). Each HFS data set is a mountable file system. The Hierarchical File System is described in the z/OS UNIX System Services User's Guide.

instruction

*(1) A statement that specifies an operation and the values and locations of its operands. (2) See also "assembler instruction", "machine instruction", and "macro instruction".

job control language (JCL)

A language used to code job control statements.

*job control statement

A statement in a job that is used in identifying the job or describing its requirements to the operating system.

language

A set of representations, conventions, and rules used to convey information.

*language translator

A general term for any assembler, compiler, or other routine that accepts statements in one language and produces equivalent statements in another language.

library macro definition

A macro definition that is stored in a macro library. The IBM-supplied supervisor and data management macro definitions are examples of library macro definitions.

linkage editor

A processing program that prepares the output of language translators to enable it to run. It combines separately produced object or load modules; resolves symbolic cross references among them; replaces, deletes, and adds control sections; generates overlay structures on request; and produces executable code (a load module) that is ready to be fetched into main storage and run.

linker

Used in this publication as collective term for binder and linkage editor.

load module

The output of a single linkage editor run. A load module is in a format suitable for loading into virtual storage and running.

loader

A processing program that does the basic editing functions of the linkage editor, and also fetches and gives control to the processed program. It accepts object modules and load modules created by the linkage editor and generates executable code directly in storage. The loader does not produce load modules for program libraries.

local dictionary

An internal table used by the assembler during macro generation to contain the current values of all local SET symbols. There is one local dictionary for open code, and one for each macro definition.

location counter

A counter whose value indicates the assembled address of a machine instruction or a constant or the address of an area of reserved storage, relative to the beginning of the control section.

*machine instruction

An instruction that a machine can recognize and execute.

*machine language

A language that is used directly by the machine.

macro definition

A set of statements that defines the name of, format of, and conditions for generating a sequence of assembler language statements from a single source statement. This statement is a macro instruction that calls the definition. (See also "library macro definition" and "source macro definition".)

macro generation (macro expansion)

An operation in which the assembler generates a sequence of assembler language statements from a single macro instruction, under conditions described by a macro definition.

macro instruction (macro call)

An assembler language statement that causes the assembler to process a predefined set of statements (called a macro definition). The statements normally produced from the macro definition replace the macro instruction in the source program.

macro library

A library containing macro definitions. The supervisor and data management macro definitions supplied by IBM (such as GET and LINK) are contained in the system macro library. Private macro libraries can be concatenated with the system macro library.

macro prototype statement

An assembler language statement that specifies the mnemonic operation code and the format of all macro instructions that are used to call a macro definition.

MACRO statement

An assembler language statement that indicates the beginning of a macro definition. (Also known as a macro definition header).

main storage

All program addressable storage from which instructions can be executed and from which data can be loaded directly into registers.

MEND statement

An assembler language statement that indicates the end of a macro definition. (Also known as a macro definition trailer).

model statement

A statement from which assembler language statements are generated during conditional assembly.

object module

The machine-language output of a single run of an assembler or a compiler. An object module is used as input to the linkage editor, loader, or binder.

open code

The portion of a source module that lies outside of and after any source macro definitions that might be specified.

*operating system

Software that controls the running of computer programs and which can provide scheduling, debugging, input and output control, accounting, compilation, storage assignment, data management, and related services (see "control program".)

ordinary symbol attribute reference dictionary

A dictionary used by the assembler. The assembler puts an entry in it for each ordinary symbol encountered in the name field of a statement. The entry contains the attributes (such as type and length) of the symbol.

Part Reference

A named subdivision of a MERGE class in a program object. A Pseudo-Register (external dummy section) or an external data item, having length and alignment attributes. Space in the loaded program is reserved for Parts (which can contain machine language text), but not for Commons or Pseudo-Registers.

partitioned data set (PDS)

A data set on direct-access storage that is divided into partitions, called members, each of which can contain a program, part of a program, or data.

PDSE (partitioned data set extended)

A system-managed data set that contains an indexed directory and members that are like the directory and members of partitioned data sets.

phase

The output of a single z/VSE linkage editor run. A phase is in a format suitable for loading into virtual storage

processing program

(1) A general term for any program that is not a control program. (2) Any program capable of operating in the problem program state. This includes IBM-distributed language translators, application programs, service programs, and user-written programs.

program

A general term for any combination of statements that can be interpreted by a computer or language translator, and that serves to do a specific function.

program fetch

A program that prepares programs for execution by loading them at specific storage locations and readjusting each (relocatable) address constant.

program library

A partitioned data set or PDSE (z/OS), or Librarian library (z/VSE), that always contains named members.

program management binder

See binder.

program module

Used in this publication as collective term for load module and program object.

program object

A new form of executable program supporting one or more independently relocatable loadable segments. Program objects are stored in PDSE program libraries, and are produced by the Program Management Binder.

pure DBCS

DBCS characters not delimited by SO and SI. These characters must be known to be DBCS by some other method, such as the position in a record, or a field type descriptor in a database environment.

real storage

The storage of a System/370 computer from which the central processing unit can directly obtain instructions and data, and to which it can directly return results.

read-only control section (RSECT)

That part of a program specified by the programmer to be a read-only executable control section. The assembler automatically checks the control section for possible coding violations of program reenterability, regardless of the setting of the RENT assembler option.

reenterable

An attribute that allows a program to be used concurrently by more than one task. This attribute is sometimes called reentrant.

refreshable

An attribute that allows a program to be replaced with a new copy without affecting its operation.

reusability

An attribute of a program that defines the scope to which it can be reused or shared by multiple tasks within an address space.

relocatable expression

An expression is relocatable if its value changes because the control section in which it appears is relocated.

relocatable value

Is the value of a term when that value changes because the control section in which it appears is relocated.

*relocation dictionary

The part of an object or load module that identifies all addresses that must be adjusted when a relocation occurs.

residence mode

An extended architecture addressing mode (RMODE) that allows a program to specify the residence mode (below 16 MB or anywhere) to be associated with a control section.

return code

A value placed in the return code register at the completion of a program. The value is established by the user and can be used to influence the running of succeeding programs or, in the case of an abnormal end of task, might be printed for programmer analysis.

section

(1) A cross-section of program object data with a single name, consisting of elements belonging to one or more classes. (2) A control section.

segment

The aggregate of all section contributions to a given class, loaded as a single entity into storage, and having its own relocation base address.

severity code

A code assigned by the assembler to each error detected in the source code. The highest code encountered during assembly becomes the return code of the assembly step.

shift-in (SI)

The shift-in (SI) EBCDIC character (X'0F') delimits the end of double-byte data.

shift-out (SO)

The shift-out (SO) EBCDIC character (X'0E') delimits the start of double-byte data.

skeleton dictionary

A dictionary built by the assembler for each text segment. It contains the global vector table, the sequence symbol reference dictionary, and the local dictionary.

source macro definition

A macro definition included in a source module, either physically or as the result of a COPY instruction.

source module

The source statements that constitute the input to a language translator for a particular translation.

source statement

A statement written in a programming language.

*statement

A meaningful expression or generalized instruction in a programming language.

symbol file

A data set used by the assembler for symbol definitions and references and literals.

symbolic parameter

In assembler programming, a variable symbol declared in the prototype statement of a macro definition.

system macro definition

Loosely, an IBM-supplied library macro definition which provides access to operating system facilities.

text

Machine language instructions and data.

text segment

The range over which a local dictionary has meaning. The source module is divided into text segments with a segment for open code and one for each macro definition.

*translate

To transform statements from one language into another without significantly changing the meaning.

trimodal program execution

A function of z/Architecture that allows a program to run in 24-bit, 31-bit, or 64-bit address mode. The addressing mode is under program control.

translate table

A table used to replace one or more characters with alternative characters.

virtual storage

Address space appearing to the user as real storage from which instructions and data are mapped into real storage locations. The size of virtual storage is limited by the addressing scheme of the computing system and by the amount of auxiliary storage available, rather than by the actual number of real storage locations.

ward

A set of DBCS characters which have the same high-order byte value. The first byte of a double-byte character is known as the ward byte. A ward contains 190 characters. Ward X'42' defines the double-byte representation of those EBCDIC characters which are in the range X'41' to X'FE'.