Text 3. Peripheral Equipment

The microcomputer has to communicate with the outside world, so that programs and data can be entered into its memory and processed information can be displayed or transmitted in some form to the microcomputer user.

There are various types of peripheral equipment that may be at­tached to microcomputers including keyboards and paper tape readers for input, and visual display units (VDUs) and printers for output. Information may be output from the microcomputer on to magnetic tape or disk for storage and re-entered when required.

Different sensors and actuators may be linked (interfaced) to the microcomputer for controlling instruments and machines.

Keyboards

A keyboard consists of a number of switches which are activated by pressure or simply by touching them. The keys are arranged as a ma­trix, so that the depression of any key can be detected by scanning the rows and columns of the matrix. Hardware may be used to sense which key has been pressed or this may be carried out by a software routine.

The layout of the keyboard may be similar to that of the con­ventional typewriter or may be designed for particular users.

Teletypewriters

Teletypewriters may be used for a number of different purposes in computer systems. For example, they may be used as terminals to transmit and receive information over telephone lines or as input/ output devices directly connected to a computer.

Teletypewriters transmit and receive information in serial form, that is, each character is converted to a bit-code, and then sent as a stream of serial data bits with start and stop control bits for each character. The characters have to be decoded when they reach the computer end.

Teletypewriters and other terminals using telephone lines require modems (modulators-demodulators) at each end, to convert the data to a form suitable for voice transmission and vice versa.

As well as having a keyboard, teletypewriters are fitted with a printing device, so that a hard copy of the information sent and re­ceived is available. Characters are printed one at a time by moving the block containing the characters across the paper from left to right. The selected character is pressed against a typewriter ribbon to give a solid shape. Speeds vary from about 10—30 characters/second.

Teletypewriters may have paper tape stations for producing out­put on to punched paper tape.

Notes

peripheral [pa'rifarol]	зовнішній
character ['kaerikta]	знак; символ; літера
user ['ju:za]	користувач
keyboard ['ki:bo:d]	клавіатура
VDU (Visual Display Unit)	дисплей

в

output —

to touch [tAtJl —

software routine [’softwea] —

matrix [meitriks] —

hardware ['hardwea] —

layout ['leiaut] —

data bit —

start and stop control bits —

as well as having a keyboard — hard copy —-

one at a time —

to give a solid shape —

paper tape station —

ихід

торкатися

програмне забезпечення

матриця

апаратне забезпечення

схема

інформаційний біт

стартові керуючі біти нарівні з клавіатурою друкована копія

один за одним

щоб зробити щільний відтиск перфострічковий прилад