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This programme looks at the ways in which information is communicated from peripherals to computer processors, and examines the control of information in store.
Metadata describing this Open University video programme
Module code and title: TM221, The digital computer
Item code: TM221; 02
First transmission date: 01-03-1975
Published: 1975
Rights Statement:
Restrictions on use:
Duration: 00:24:24
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Producer: Ted Smith
Contributors: John Monk; Ian Witten
Publisher: BBC Open University
Keyword(s): Analogue to digital conversion; Digital computing; Information transfer; Internal structure; Oscilloscope; Parallel coding; Serial coding
Footage description: John Monk introduces as the subject of the programme computer peripherals and processors. He uses a large model of the OPUS mini-computer peripherals to demonstrate how data is transferred from the keyboard to the processor. Using a voltmeter, he measures the pattern of voltage pulses that pass from keyboard to processor in the form of parallel binary coding. Ian Witten explains serial binary coding with the help of a tele-typewriter computer terminal and an oscilloscope. He demonstrates the way in which teletype characters produce a binary pattern of voltage pulses which can be registered as a trace on the oscilloscope. Monk introduces a third type of peripheral, which converts voltage to a digital representation. He uses a chart to demonstrate the use of interval coding, by which voltage can be put into a form suitable for the processor. With the aid of an Analog-to-Digital Converter he shows how the voltage intervals are converted to a binary representation, which can be handled by a digital computer's processor. This is parallel coding. Witten uses a model to demonstrate the input of data from OPUS peripherals to a combinational element processor. He shows how digital input is read by the processor as a binary code and then returned to digital output in the form of a Minitron. With Monk's assistance he shows the processor adding numbers. Witten also explains how the designer of the machine can control the range of possible calculations. An animated diagram is used to explain the operation of a computer store in holding and retrieving data. The diagram shows control of the store through a selection device, storage elements and storage addresses. Both input and output operations are shown. Witten then uses an illuminated graphics board to demonstrate the flow of data through the computer in a simple program. The operation of the store, arithmetic unit, accumulator, and input and output peripherals on instructions is shown. Witten shows how the instructions themselves can be held in a store, enabling the computer to work automatically. Monk concludes the programme by stating briefly the subject of the following programme.
Master spool number: 6HT/71584
Production number: 00525_5162
Videofinder number: 1460
Available to public: no