# nyuller

A C64 programming project using [Oscar64](https://github.com/drmortalwombat/oscar64)
as the cross-compiler. Oscar64 is checked in as a git submodule under
`./oscar64/`.

## Layout

```
.
├── 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

```sh
# 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

```sh
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.