The Plus/4 was a dark grey business-minded machine with a word processor, spreadsheet, database and graphics program built into its memory. It also had a fast BASIC with commands for graphics and sound, and four cursor keys laid out in a diamond.
It couldn't run Commodore 64 games and was a flop in America, but it sold cheaply across Europe, where it found many fans in Hungary especially.
One chip, the TED, handled the picture, the sound and the timers. It had 121 colours: 15 hues at eight brightnesses plus black, more than any rival, and all of them could be on screen. Its modes matched the C64's, including 160x200 multicolour with wide pixels, but there were no hardware sprites, so games drew everything by hand.
Two voices of square wave. The second could play white noise instead. It was simple compared with the C64's SID.