GnuCOBOL -fdec - DEC/VSI COBOL Language Extensions

Overview

-fdec is a compatibility mode built into Sector7's GnuCOBOL compiler that lets DEC and VSI COBOL source code, written for OpenVMS, compile and run on Linux. It recognises the VMS-specific syntax, storage rules, and status conventions those programs rely on, so applications that call OpenVMS RTL routines or depend on RMS-style file handling can be rebuilt without rewriting the source.

The flag is a single, explicit gate: with -fdec off, every extension it enables becomes a compile-time error rather than a silent reinterpretation, so a standard COBOL program compiles identically whether or not the flag is used. Where Linux cannot reproduce an OpenVMS-specific mechanism exactly, such as link-time symbol resolution or VAX floating-point formats, the compiler takes the practical Linux equivalent and documents the difference instead of pretending to be VMS.