The Commodore Plus/4 was originally called Commodore 264. It was a personal computer introduced by Commodore Business Machines Inc in 1984. The Commodore 264 series was CBM's next line of computer after the Commodore 64.

The Plus/4 (or plussy, as it is affectionately called by its fans) got its name from the built-in software, developed by Tri Micro. It was called 3-Plus-1, and it was intended to be a business suite, but was bad, no matter how you look at it. (E.g. the word processor was only capable of using 99 lines.)

The plussy had 64K RAM, 121 colors, 2 voice channels and it was equipped with Commodore Basic V3.5. It's 99% compatible with it's little brothers, then C16 and the C116.

The Plus/4 wasn't nearly as successful as the C64. In the early years, all software companies developed 16K games only (instead of using the full 64K), so that those games could be sold for both the C16 and the Plus/4. Because of this, quality suffered, of course. This machine sold very well in Hungary. It was used in schools, and some companies even produced a Hungarian Plus/4 variant complete with a Hungarian keyboard. It still has a devoted demoscene.