Structure of Computers and Computations
Structure of Computers and Computations
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In the design of early computing systems it was usual to provide for only a minimum of input and output devices, such as paper tape (q.v.) or card readers and punches, and perhaps a line printer. All these peripherals were essentially slow. In such cases, data could be transferred to and from the peripheral, character by character, and each unit had its special input or output line. Normally, data transferred between an input-output (I/O) device and memory passed through the processor. Later it was found necessary to provide many I/O devices. With the advent of magnetic tape and disk units, which are faster devices with short crisis times (i.e. a need to be serviced very quickly if data was not to be lost), multicharacter block transfers became necessary.