How Steve Wozniak Built the First Complete Computer System Solo in 1976

Background

In 1975 the Homebrew Computer Club meeting inspired Steve Wozniak to design a complete computer system by himself, handling both hardware and software.

Hardware configuration

CPU: Motorola 6800 microprocessor (off‑the‑shelf).

Memory: 4 KB static RAM, address range 0x0000‑0x0FFF.

Video output: optional composite via a shift register.

Storage interface: cassette tape for loading programs.

Software – machine language monitor

The Apple I shipped without a full operating system. Instead it included a 256‑byte machine‑language monitor that acted as a primitive shell. The monitor provided three core functions:

Enter and edit machine code in hexadecimal.

Examine memory contents at arbitrary addresses.

Execute a program starting at a user‑specified address.

The monitor resides at the top of RAM (e.g., $FF00‑$FFFF) and can be invoked with a command such as CALL $FF00.

Development process

Wozniak designed the circuit board, wrote the monitor in assembly language, and created a BASIC interpreter that could be loaded from cassette. All components—CPU, RAM, TTL logic chips—were purchased as standard parts; the design used a simple bus with address decoding implemented by a few logic gates.

Commercialization

The Apple I was introduced in July 1976 at a price of US $666.66. About 200 units were sold before the Apple II, released in 1977, superseded it.

Legacy

The project shows that a single engineer can integrate existing hardware and write low‑level software to produce a functional computer. Modern commercial processors, memory subsystems, and operating systems involve extensive design, verification, and optimization that require large teams, making a comparable one‑person effort impractical today.