Xerox Alto
Hard Drive Recovery - Xerox Alto
The Xerox Alto was a personal computer developed by Xerox PARC in 1973. The idea was first conceptualized in 1972 by Butler Lampson and was designed primarily by Chuck Thacker. The Alto was used to control external disk drives to act as a file server. This was a common application for the machine.
Xerox Alto was the first computer to use the desktop metaphor and graphical user interface (GUI). It had a bit-slice processor based on the Texas Instruments’ 74181 chip and had 128 (expandable to 512) kB of main memory and a hard disk that used a removable 2.5 MB single-platter cartridge.
Alto’s CPU was an innovative micro-coded processor that used microcode for most of the I/O functions rather than hardware functions. The microcode machine had 16 tasks, of which one executed the normal instruction set. Others were used for display, memory refresh, disk, network and other I/O functions.
Alto featured both Ethernet and a bi-level CRT display as the output device. Input devices were custom detachable keyboard, a three-button mouse and an optical 5-key chord keyset. The keyboard was special in that each key was represented as a separate bit in a set of registers. This characteristic was used to alter where the Alto would boot from. Several other I/O devices were developed for Alto. They include a TV camera, the Hy-Type daisywheel printer and a parallel port.
Early software for the Alto was written in the BCPL programming language, and later in the Mesa programming language.
