REXX/370

REXX Interpreter for MVS 3.8j — Interface-compatible with IBM TSO/E Version 2 REXX

Overview

REXX/370 is a from-scratch implementation of a REXX language interpreter for MVS 3.8j, designed to be interface-compatible with the TSO/E Version 2 REXX specification (SC28-1883-0, December 1988).

Design Goals

• IBM Interface Compatibility — Identical control block layouts (ENVBLOCK, PARMBLOCK, EXECBLK, INSTBLK, EVALBLOCK, SHVBLOCK), compatible IRXxxxx programming services, compatible replaceable routine interfaces
• Reentrant — All modules RENT, all working storage via GETMAIN, no static data modification. Multiple concurrent REXX environments in the same address space.
• Embeddable — Usable from HTTPD (CGI), ISPF, UFSD, Batch, STCs via replaceable I/O routines (SAY/PULL hooks)
• SAA Procedures Language Compliance — Full REXX language as defined by SAA CPI

Non-Goals (for now)

• DBCS support (Appendix B — deferred)
• ISPEXEC / ISREDIT integration (requires ISPF)
• 31-bit addressing (MVS 3.8j is 24-bit only)

Project Structure

rexx370/
  inc/            C headers
    irx.h           IBM-compatible control block definitions
    irxanchr.h      ECT-slot anchor API + IRXANCHR registry structs/prototypes
    irxwkblk.h      Internal Work Block (per-environment interpreter state)
    irxfunc.h       Service function prototypes
  src/            C source (CRENT370)
    irxstor.c       Storage Management Replaceable Routine
    irxinit.c       IRXINIT - Environment Initialization
    irxterm.c       IRXTERM - Environment Termination
    irx#anch.c      ECTENVBK anchor: push on IRXINIT, pop on IRXTERM
    irxuid.c        User ID Replaceable Routine
    irxmsgid.c      Message ID Replaceable Routine
  mac/            HLASM macros and DSECTs
    irxenvb.mac     ENVBLOCK DSECT
    irxparm.mac     PARMBLOCK DSECT
  test/           Test programs
    test_phase1.c   Phase 1 smoke test
  doc/            Documentation
    workpackages.md Work package descriptions for implementation
  jcl/            Sample JCL
  build/          Build artifacts
  project.toml    Build configuration

Build

Requires: c2asm370, CRENT370, HLASM (for macros)

mbt build

Architecture

See: REXX/370 Architecture Design v0.1.0 and the Notion Concept Page

References

• SC28-1883-0: TSO/E V2 REXX Reference (December 1988) — Primary specification
• SC28-1882: TSO/E V2 REXX User's Guide
• SC26-4358: SAA CPI Procedures Language Reference
• GC28-0684: MVS/370 System Programming Library: Supervisor

License

(c) 2026 mvslovers