sw-cor24-fortran

Fortran compiler for the COR24 24-bit RISC ISA (future/research).

Part of the COR24 ecosystem.

FTI-0
A small educational FORTRAN subset compiler in SNOBOL4 targeting PL/SW.

Overview

sw-cor24-fortran is an experimental educational compiler project.

The first language subset is FTI-0:

• a small, fixed-form, integer-only FORTRAN-like subset
• implemented in SNOBOL4
• targeting PL/SW
• designed for clarity, testability, and historical flavor rather than full FORTRAN compatibility

The initial goal is to compile small educational programs such as:

• integer assignment
• simple expressions
• GOTO
• counted DO
• PRINT
• READ
• one-dimensional integer arrays

The project is intentionally staged:

1. normalize and parse fixed-form source
2. build symbols and resolve labels
3. lower control flow to a simple normalized form
4. emit readable PL/SW
5. later revisit floating point and richer FORTRAN features

Live demo: hello world

A working Hello, World! end-to-end demo is live, even though the full FTI-0 compiler is still under construction:

scripts/fortran examples/hello.f > /tmp/hello.s
cor24-asm /tmp/hello.s -o /tmp/hello.lgo
cor24-emu --lgo /tmp/hello.lgo --quiet --speed 0
# prints "Hello, World!"

For now, scripts/fortran short-circuits examples/hello.f to a hand-written examples/hello.s (Path A per tools/briefs/dcftn-fortran-hello-world.md). The pre-built examples/hello.lgo is the demo deliverable that the dwftn web frontend will embed.

Run scripts/test-hello.sh to regression-check the pipeline.

The full FTI-0 compiler (the SNOBOL4-based pipeline that consumes arbitrary .f sources) is a separate parallel effort -- see docs/snobol4-blockers.md for status.

Status

This repository currently defines:

• the project structure
• the FTI-0 language subset
• the compiler architecture
• the PL/SW mapping contract
• the milestone plan
• a Path-A hello-world fixture (examples/hello.s + examples/hello.lgo)

Compiler implementation is expected to begin with source normalization and statement classification.

Repository structure

• docs/ -- product, architecture, design, plan, subset definition
• snobol4/ -- compiler source and tests
• examples/ -- sample FTI-0 input programs
• plsw/ -- runtime helpers and generated output
• scripts/ -- development helpers

First milestone

The first executable milestone is:

• accept a tiny .f source file
• normalize fixed-form statements
• classify statements
• dump normalized statement records

No code generation is required for the first milestone.

Naming

• Repository: sw-cor24-fortran
• Subset language: FTI-0
• Compiler executable: fti0c

Non-goals for FTI-0

FTI-0 does not initially support:

• floating point
• FORMAT
• COMMON
• EQUIVALENCE
• statement functions
• separate compilation
• optimization
• multidimensional arrays
• full FORTRAN compatibility

Long-term direction

Possible later stages include:

• richer FORTRAN subset levels
• arithmetic IF
• subroutines and functions
• software floating point
• direct or indirect lowering into COR24-oriented toolchains

Research

See docs/research.txt for detailed design research and historical context.

Related Repositories

Repository	Description
sw-cor24-emulator	COR24 emulator + ISA
sw-cor24-x-assembler	COR24 assembler
sw-cor24-project	Ecosystem hub

Links

• Blog: Software Wrighter Lab
• Discord: Join the community
• YouTube: Software Wrighter

Copyright

Copyright (c) 2026 Michael A. Wright

License

MIT License. See LICENSE for the full text.