Following on from the success of the C64, Commodore set about creating a system to replace the ageing VIC-20 - itself still in production - and potentially replacing the C64 itself with something cheaper. The 264 series was born, split into three variants: the largely-unknown-outside-Europe 116, the 16, and the Plus/4. While the former two featured just 16KB of RAM, the latter boasted a full 64KB; plus a 4-programme office suite in ROM (from which it derived its name).
Sadly, for all it did right, it did far too much wrong to make a name for itself. While it had twice the clock speed, more colours to choose from, stereo sound, and even more usable RAM (approximately 60KB was free in BASIC), it cost as much as the established C64, couldn't run the majority of existing Commodore software, had a fractured market due to the 16KB variants, lacked sprite and sound modulation capabilities, and inexplicably changed nearly every external interface to one that was physically incompatible with existing peripherals.
The entire 264 line was discontinued in 1985 - the year after its introduction.