In 1979 Apple begins work on "Sara", the code name for what will be the Apple III.
The Apple III was announced May 19, 1980, during the National Computer Conference (NCC) in Anaheim California.
Price ranges from US$4500 to US$8000.
In the fall of 1980 Apple ships the first Apple III units in limited quantity.
It ran a Synertek 6502A processor running a new operating system named Apple SOS at 2 MHz, twice as fast as the Apple II. It had a maximum of 128k of RAM, twice the memory of an Apple II.
It was also the first Apple computer to have a built-in floppy drive, a Shugart 143k 5.25" disk drive.
It could have two additional peripherals added via its two serial ports, and had 4 internal expansion slots that were compatible with Apple II cards. But Steve Jobs, who supervised the project gave ridiculous demands to the development team including dimensions that were too small to fit all the components, and no cooling fan. The result was that the team had to cram the components in allowing little or no ventilation. Since there was no fan to cool the overheating, the chips expanded and eventually popped out of the machine, killing it.
After replacing 14,000 bad IIIs, a newly revised Apple III, with 256k RAM and the option of adding a 5MB ProFile hard drive for $3495, was released late in the fall of 1981.
In December 1983, Apple introduces the redesigned Apple III as the Apple III+, for US$3000. It had 256k RAM, a working logic board with built-in clock, improved peripheral ports with standard DB-25 connectors, a modified slot for easier card installation, and Apple SOS 1.3.
Nevertheless, the III had a very bad reputation by this time and it was inevitably "too little, too late".
The Apple III was retired on April 24, 1984 with only 65,000 units sold in total.

Apple ///
  • Sn; A3S2-117207
  • CPU; 6502A, 2MHz
  • RAM; 256 K
  • Floppy drive; built-in Shugart 143K 5.25"
  • 80 Column display.
  • Graphics; 16 shades of green with 192x560 dots.
  • Color; 16 colors with 192x280 dots.
  • Sound; 64 volume settings and over seven octaves.
  • Speaker; Speech producing quality.
  • Real time clock (location 3-B on mother board).
  • Diagnostics in ROM.
  • O/S; SOS 1.1 dated 1-Feb-82
Monitor ///
  • Model; A3M0039
  • Sn; B2K 144034

The back of the Apple ///

Side view

Inside view
The project was code named "Sara" after the daughter of Chief Engineer Wendell Sander. The III's OS was called "Sara's Operating System" before it was changed to it's more formal Apple Sophisticated Operating System (better known as SOS).
After the presentation of the Apple III at NCC, Apple transported 7,000 people that attended the event to nearby Disneyland. Apple had rented out the theme park for 5 hours at a cost of $42,000. Although Apple's official name for the Apple III OS is Apple SOS, most users  began to call it S-O-S, like the emergency distress call. This was obviously because of the computers severe problems. Steve Jobs, weary of the mess he had done with the Apple III project, tried to distance himself from the Apple III by "hovering" over the Lisa project which coincidentally was Apple's second failure.
For more information see the APPLE /// FAQ's