Z software Z developer tools High Level Assembler and Toolkit IBM High Level Assembler and Toolkit Feature
Improve programmer productivity and simplify program development and maintenance with this assembler and optional toolkit
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IBM High Level Assembler (HLASM) and Toolkit Feature is a flexible development solution for all Assembler Language applications. The assembler and optional toolkit improves programmer productivity and simplifies program development and maintenance. 

HLASM provides all the proven facilities found in earlier assemblers and includes many new facilities. It helps you develop programs and subroutines for functions not typically provided by other symbolic languages, such as COBOL, FORTRAN, and PL/I. High Level Assembler provides extensions to the basic assembler language, and the macro and conditional assembly language, including external function calls and built-in functions. The optional High Level Assembler Toolkit Feature is a powerful and flexible set of tools that enhances application recovery and development.

Benefits Efficient

Enhanced usability with warning-suppression option.


Simplified tool integration with improved SYSADATA record layouts.


Cross-system compatibility assisted by ASCII constants.


Simplified macro coding with longer macro arguments and string variables.

Changed Assembler instructions

QY-type and SY-type address constants provide resolution into long-displacement. Support for three decimal floating-point data types, increasing instruction addressability and reducing the need for additional instructions.

Unified Opcode table

OPTABLE option – The OPTABLE option is permitted on the *PROCESS statement.

Mnemonic tagging

Suffix tags for instruction mnemonics let you use identically-named macro instructions and machine instructions in the same source program.

Programming and diagnostic aids

HLASM provides assembler listing and diagnostic features to help program development and analysis of program errors. A comprehensive assembler listing provides details about a program and its assembly. Assembler options help control the format of the listing and which sections to produce.

Macro language extensions

The macro language is an extension of the assembler language. It provides a convenient way to generate a preferred sequence of assembler language statements many times in one or more programs. HLASM supports macro definition and macro instruction.

Conditional assembly extensions

Flexible extensions for external function calls, built-in functions, extensions to existing instructions and SET symbol usage, system variable symbols, and data attributes.

Technical details

System requirements

High Level Assembler runs under these operating systems. Unless otherwise stated, the assembler also operates under subsequent versions, releases, and modification levels of these systems:

  • OS/390® Version 2 Release 10.0
  • VM/ESA Version 3 Release 1.0
  • z/VM® Version 5 Release 2
  • VSE/ESA Version 2 Release 6
  • z/VSE® Version 3 Release 1 andVersion 4
  • z/OS® Version 1 Release 2.0
System requirement details

Machine requirements

For assembling and running High Level Assembler programs, tape device and double-byte data requirements, see the machine requirements.

Machine requirement details

Storage requirements

For virtual storage, auxiliary storage space, library space and installation, see the storage requirements.

Storage requirement details
Resources Interactive Bug Facility User Guide

Interactive Debug Facility (IDF) is a symbolic debugging tool for most high-level languages.

Installation and Customization Guide

A guide to installation and customization of High Level Assembler and Toolkit Feature.

Toolkit Feature User's Guide

Learn how to use structured programming macros, disassembler, program understanding tool, cross-reference facility and enhanced SuperC components of the Toolkit feature.

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Next steps

Discover how to improve programmer productivity and simplify program development and maintenance with IBM High Level Assembler and Toolkit Feature. Schedule a no-cost 30-minute meeting with an IBM Z or Power representative.

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