The Commodore VIC-20 was the predecessor of the Commodore 64 and as such one of the first home computers. The VIC-20 was released in 1980 and was the first computer to sell a million units.
The VIC-20 was intended to be a cheaper version than the PET computer. It was equipped with the same MOS 6502 processor and had 5kB of onboard memory, of which 3.5kB was available as user memory. The RAM was expandable with an external cartridge of, for example, 16kB.