English Electric KDF8 - Computer Operation

Computer Operation

The KDF8 operator interface could with hindsight fairly be described as both asymmetrical and challenging. It required a very high level of skill, perhaps not often recognized appropriately at the time. As has been stated, there was essentially NO operating system. A very small (about 20 instructions) bootstrap loader could be held at the front of each program tape, but even this approach was not always used. Tape labels were (with the exception of COBOL and Tape Control managed applications) almost non-existent. A grandfather/father/son cycle of tape rotation protected production tapes from major disasters, but required careful manual controls. Programmers (or for operational suites Production Control staff) gave the operator written instructions on which program tape and data tapes to load, on which devices, and a written summary of how to load and initiate each program. The operator would then load the tapes, and load and initiate each program in turn manually from the console.

The console consisting of a vertical display panel about 10 inches (250 mm) high by about 5 feet (1.5 m) long with a similarly sized slightly angled control panel below it. Each of these two parts was filled with labeled buttons and illuminated indicators each (roughly) one inch square. The display section was made up of indicators which when illuminated showed, in binary (grouped as octal) characters, the machine’s current running (or static) status at the individual machine core address and register level, for the compute, read and write operations then in progress. When a program was running, this display was a kaleidoscope of quickly changing, flashing, multi-colored lights. The control panel section consisted of press-buttons to select the next register to be set and a central part that mirrored the lay-out of a single machine core address. Other buttons accessed more complex(!) operations. Use of these buttons enabled the operator to select and then directly input to the machine’s core storage locations and registers the octal pattern he/she keyed in manually. For an operator to input a single machine instruction, each of up to ten octal characters of the instruction had to be selected and keyed in as its binary pattern – each with the correct (odd) parity bit! A skilled operator would “play” the console like a pianist, entering codes faster than the uninitiated observer could follow.