The first machine from the newly Jack Tramiel (he of Commodore fame) powered Atari was this, the 520ST. ST in this case stood for Sixteen/Thirty-32 since it was a 32-bit powered machine with a 16-bit data bus. A ROM-based OS called TOS (The Operating System) and MIDI ports came as standard but nothing else did - PSU, 720k single sided SF354 floppy drive (with its own power brick) and monitor were all necessary extras. Let the playground arguments commence...