The HLASM Toolkit Feature Interactive Debug Facility (IDF) supports a rich set of capabilities that speed error detection and correction. Although IDF is intended primarily for debugging assembler language programs on z/OS, z/VM, and z/VSE, you can also use it to debug programs written in most high-level languages.

• IDF provides multiple selectable views of a program, including separate windows for address stops, breakpoints, register displays, object code disassembly, storage dumps, language-specific support, register histories, non-traced routines, and other information. You can use these views in any order or combination.
• You can control execution of a program by stepping through individual instructions or between selected breakpoints or routines.
• If source code is available (which is almost always the case for programs assembled with HLASM), IDF can display source statements as it executes the program.
• The power of IDF is greatly magnified by its ability to pass control from any breakpoint to user exit routines written in REXX or other languages that can capture and analyze program data, and respond dynamically to program conditions.
• You can count instruction executions, and IDF can maintain an instruction execution history.
• You can dynamically modify storage areas and register contents during debugging by typing new values on the displays.
• IDF supports a special class of conditional breakpoints called watchpoints, which IDF triggers only when a user-specified condition occurs.
• A command-level record and playback facility allows a debugging session to be re-executed automatically.
• Extensive tailoring capabilities allow you to establish a familiar debugging environment. Most debugging actions can be easily controlled by PF-key settings.