3 April

The Osborne 1 was the first commercially successful portable microcomputer, released on this day in 1981 by Osborne Computer Corporation.

It weighed 10.7 kg (23.5 lb), cost $1,795 USD, and ran the CP/M 2.2 operating system. It was powered directly from a mains socket as it had no on-board battery, though it was still classed as a portable device as it could be packed away and transported by hand to another location. The computer shipped with a large bundle of software that was almost equivalent in value to the machine itself, a practice adopted by other CP/M computer vendors at the time.

Hardware configuration:

  • Dual 5¼-inch, single-sided 40 track floppy disk drives (“dual density” upgrade available)
  • 4 MHz Z80 CPU
  • 64 kilobytes main memory
  • Fold-down 69 key detachable keyboard doubling as the computer case’s lid
  • 5-inch, 52 character × 24 line monochrome CRT display, mapped as a window on 128 × 32 character display memory
  • IEEE-488 port configurable as a Parallel printer port
  • RS-232 compatible 1200 or 300 baud Serial port for use with external modems or serial printers