How Many Kilobytes of ROM Did the VIC-20 BASIC Use

The Commodore VIC-20 remains a landmark machine in the history of home computing, known for being the first computer to sell one million units. While many enthusiasts recall its limited RAM, the read-only memory architecture is equally critical to its operation. This article provides a technical breakdown of the VIC-20 memory map, specifically identifying the exact amount of ROM allocated to store the BASIC programming language interpreter.

The system utilized a MOS Technology 6502 microprocessor and came equipped with a total of 16 kilobytes of ROM. This non-volatile memory was essential for storing the firmware required to boot the machine and manage hardware interactions. Within this 16 KB structure, the memory was divided primarily between the operating system kernel and the programming environment.

Specifically, the Commodore VIC-20 contained 8 kilobytes of ROM dedicated to its BASIC interpreter. This 8 KB block allowed users to write and execute programs in BASIC immediately upon powering on the device. The remaining 8 kilobytes of ROM were reserved for the Kernal operating system and character generator routines, ensuring the 8 KB BASIC allocation was a precise half of the total read-only memory available on the motherboard.