CHIP-8 Emulator

A simple, from scratch implementation of the CHIP-8 virtual machine, written in C with SDL2 for graphics and input.

What is CHIP-8?

CHIP-8 is a virtual machine, created in the mid-1970s by Joseph Weisbecker to make it easier to write games for early microcomputers such as the COSMAC VIP.

CHIP-8 programs were small, simple, and portable. Many classic games like Pong, Breakout, and Space Invaders were written for CHIP-8.

CHIP-8 Architecture Overview

• Memory: 4096 bytes (4 KB)
• Program start address: 0x200
• Registers:
  • 16 general-purpose 8-bit registers (V0–VF)
  • VF is also used as a flag register
• Index register: I (16-bit)
• Program counter: PC
• Stack: used for subroutine calls
• Display: 64 × 32 monochrome pixels
• Timers:
  • Delay timer
  • Sound timer

Keyboard Layout

Original CHIP-8 keypad:        Mapped keyboard keys:

1 2 3 C                        1 2 3 4
4 5 6 D        --->            Q W E R
7 8 9 E                        A S D F
A 0 B F                        Z X C V

Dependencies

This project depends on:

• SDL2 — for window creation, rendering, and keyboard input

Installing SDL2 (macOS with Homebrew)

brew install sdl2

Verify installation:

which sdl2-config

Building the Emulator

From the project root:

make

This will produce an executable named:

chip8

Running the Emulator

Run the emulator from the terminal and pass a CHIP-8 ROM:

./chip8 path/to/rom.ch8

Example:

./chip8 roms/PONG.ch8

Project Goals

• Implement the CHIP-8 instruction set faithfully
• Keep the codebase simple and readable
• Make all machine state explicit

This project is intentionally written in plain C, without object systems or heavy abstractions, to keep the machine model visible.

TODO

• Implement audio output (beep when sound timer > 0)
• Improve timing accuracy

References

• Cowgod’s CHIP-8 Technical Reference