.
├── oscar64/        # Oscar64 cross-compiler (git submodule)
├── docs/c64/       # Low-level C64 reference (memory map, VIC, CIA, SID, …)
├── src/            # Your C code
│   ├── helloworld.c
│   └── build.sh    # Compile + run helper
├── OSCAR64.md      # Notes on the Oscar64 compiler internals
└── PROG_C64.md     # Notes on programming the C64 hardware

First-time setup

# 1. Clone with submodules:
git clone --recurse-submodules <this-repo-url>

# Or, if you already cloned without --recurse-submodules:
git submodule update --init --recursive

Building

cd src
./build.sh            # compile helloworld.c → src/build/helloworld.prg
./build.sh -e         # run in oscar64's built-in emulator (fastest)
./build.sh -v         # run in VICE x64 (standard, fast)
./build.sh -V         # run in VICE x64sc (cycle-exact, slow but bit-perfect timing)

build.sh will build the oscar64 compiler automatically the first time (it runs make -C make compiler inside ./oscar64/ if ./oscar64/bin/oscar64 doesn't exist yet).

VICE 3.9 is installed at /usr/bin/ and provides x64, x64sc, x128, xvic, xpet. We target the C64, so x64 (fast) and x64sc (cycle-exact) are the two we use. x64sc is the one that matches real-hardware timing for the raster IRQ and SID tests.

Documentation

PROG_C64.md — how the C64 hardware actually works, from a low-level programming perspective. Start here if you want to understand what's going on under the hood.
OSCAR64.md — how the Oscar64 compiler works internally, plus a C64- specific section on how to use it well (memory model, bank switching, raster IRQs, common mistakes).
docs/c64/ — downloaded reference material: the full Commodore 64 Programmer's Reference Guide text, Christian Bauer's canonical VIC-II paper, and per-chip reference notes.