The z390 Portable Mainframe Assembler and Emulator is a Java-based, open-source development tool that allows you to write, compile, link, and execute IBM High-Level Assembler (HLASM) and COBOL programs on a local PC. Created originally by Don Higgins, it provides a lightweight alternative to full-scale emulators like Hercules or expensive live mainframe environments.
Mastering this environment gives programmers a fast, localized platform for learning mainframe syntax, performing regression testing, and preparing code before deploying it to an actual z/OS environment. Core Architecture and Features
The environment translates IBM mainframe instructions into executable logic via Java, removing the need for a native z/OS operating system.
HLASM Compatibility: It features an assembler and linkage editor highly compatible with IBM’s High-Level Assembler syntax and standard macro definitions.
zCobol Compiler: It includes a subset compiler capable of translating COBOL programs into assembler code, which is then processed by the z390 engine.
File Emulation: It natively handles Queued Sequential Access Method (QSAM) for sequential data, as well as Virtual Storage Access Method (zVSAM) for indexed dataset structures.
Interactive Middleware Emulation: It features basic runtime support for Customer Information Control System (zCICS) interactive application testing. Key Components of the Environment
Navigating z390 requires understanding its primary file structures and command tools. z390/README.md at main · z390development/z390 – GitHub
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