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aurielsolaris/f9s

Analysis updated 2026-08-08 · repo last pushed 2026-03-28

CAudience · developerComplexity · 4/5MaintainedSetup · moderate

TLDR

F9S is a tiny custom programming language inspired by FORTRAN 95 that compiles code directly into Windows executables, written in under 3,500 lines of C with no external compiler frameworks.

Mindmap

mindmap
  root((repo))
    What it does
      Compiles to Windows exe
      Interactive math REPL
      Variables loops arrays
      Hashmaps for lookups
    Tech stack
      Written in C
      x86-64 machine code
      SSE and AVX support
      Command-line interface
    Use cases
      Learn how compilers work
      Experiment with FORTRAN syntax
      Quick math calculations
      Build small Windows programs
    Audience
      Compiler enthusiasts
      Language hobbyists
      Students of compilers
    Design choices
      Under 3500 lines
      Pat and slap errors
      64-slot hashmaps
      FORTRAN 95 subset

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What do people build with it?

USE CASE 1

Learn how compilers work by studying a compact codebase that goes from source code to machine instructions.

USE CASE 2

Experiment with a simplified FORTRAN-like syntax in a lightweight interactive environment.

USE CASE 3

Type quick math expressions at the command line and get instant answers.

USE CASE 4

Write small programs with loops, arrays, and hashmaps that compile to standalone Windows executables.

What is it built with?

Cx86-64 AssemblyFORTRAN 95SSEAVX

How does it compare?

aurielsolaris/f9s0verflowme/radare2ac000/find-flv
LanguageCCC
Last pushed2026-03-282026-07-022013-04-05
MaintenanceMaintainedMaintainedDormant
Setup difficultymoderatemoderatemoderate
Complexity4/54/52/5
Audiencedeveloperdeveloperdeveloper

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · moderate Time to first run · 30min

Requires a Windows environment with an x86-64 processor and a C toolchain to build the compiler from source.

No license information is provided in the repository, so usage rights are unclear.

In plain English

F9S is a small, custom programming language based on a simplified version of FORTRAN 95. It lets you write simple programs with variables, loops, arrays, and hashmaps (key-value lookup tables), then compiles them directly into standalone Windows executables. You interact with it through a command-line prompt where you can either compile files or just type quick math expressions like 3 + 2 to get instant answers. When you feed it a source file, the compiler reads your code and translates it into raw machine instructions for x86-64 Windows processors. Notably, it handles some of the arithmetic using assembly code written directly for the CPU, and it even checks your hardware at startup to see if it supports advanced math features like SSE or AVX for faster square root calculations. If your CPU doesn't support those features, it falls back to a clever software workaround. This project would appeal to someone learning how compilers actually work under the hood, since the entire thing is under 3,500 lines of code and is built from scratch rather than relying on existing compiler frameworks. It is also a fun tool for anyone who likes the classic syntax of FORTRAN but wants a lightweight environment to experiment with basic programming concepts like control flow, arrays, and hashmaps. The project makes some deliberate tradeoffs worth noting. It is not a complete implementation of FORTRAN 95, it covers a curated subset of the language's features. The error reporting uses a lighthearted "pat" (warning) and "slap" (error) system to give you feedback, and the hashmaps are relatively simple 64-slot tables rather than fully dynamic data structures. These choices keep the project compact and understandable rather than aiming for production-grade robustness.

Copy-paste prompts

Prompt 1
Help me write a simple F9S program that uses a loop to fill an array with numbers and then prints the sum, using FORTRAN-like syntax.
Prompt 2
I have the F9S compiler cloned, walk me through compiling a basic .f9s source file into a Windows executable from the command line.
Prompt 3
Show me how to use the F9S interactive prompt to evaluate a math expression like 3 + 2 and then write a small program using variables and a hashmap.
Prompt 4
Explain how the F9S compiler detects SSE or AVX support at startup and what happens if my CPU does not have those features.
Prompt 5
Write an F9S program that uses a hashmap to store key-value pairs and then looks up a value by its key, printing the result.

Frequently asked questions

What is f9s?

F9S is a tiny custom programming language inspired by FORTRAN 95 that compiles code directly into Windows executables, written in under 3,500 lines of C with no external compiler frameworks.

What language is f9s written in?

Mainly C. The stack also includes C, x86-64 Assembly, FORTRAN 95.

Is f9s actively maintained?

Maintained — commit in last 6 months (last push 2026-03-28).

What license does f9s use?

No license information is provided in the repository, so usage rights are unclear.

How hard is f9s to set up?

Setup difficulty is rated moderate, with roughly 30min to a first successful run.

Who is f9s for?

Mainly developer.

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