wtf is f9s?

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.