Тексты компьютерной и информационной сферы для перевода с английского языка (Magnetic tapes. Reel-to-reel tape. Cartridge tape. Access of information), страница 2

a)  fixed disk is a popular component for use with PC's. The hard disk is installed inside the computer and is never handled by the user.

b)       The disk-on-a-card is a cheaper alternative to a fixed hard disk. The card, a plastic sheet containing an amount of circuitry and the disk, is fitted into one of the expansion slots inside the microcomputer. Expansion slots are rectangular sockets located inside the computer,
and are used for connecting peripheral devices to the CPU.

Find out how much information each type of disk can store and rank them in order of size. Find out the costs of installing each one of the three hard d sks and decide which of the three is tne best value for money.

c)       A Bernoulli box is the hard disk equivalent of the removable
floppy diskette. The disk is contained inside a plastic cartridge that can
be inserted into and removed from a disk drive in the same way as
a floppy diskette. The advantages of the Bernoulli box are two-fold.
First, hard disk amounts of information can be accessed at hard disk
speeds and second, like the floppy diskette, the drive is available for use
with as many disks as desired. The Bernoulli box is not a true hard disk.
It is a pliable plastic disk enclosed within an aerodynamically designed
cartridge which employs a principle of aerodynamics first discovered by
James Bernoulli in the 19th century. The principle is that when a pliable
object is rotated within a specially designed cavity it becomes rigid and
in this way takes on the features of a hard disk. Bernoulli boxes are
available for use with microcomputers and greatly increase the amounts
of useful information available to them

Find out how much information each type of disk can store and rank them in order of size. Find out the costs of installing each one of the three hard d sks and decide which of the three is tne best value for money.

The disk pack

21      The disk pack is used with larger computer systems. It consists of a number of hard disks fixed on top of each other and all enclosed in a plastic container. The disk pack is removable and is a very popular means of secondary storage for the larger computer systems.

Information stored on magnetic media is measured in alphanumeric characters. We shall see later that these are called BYTES. Find out how many bytes each of the different types of magnetic disks can store.

Optical disks and cards

22   Optical disks have emerged from the compact disk technology originally developed for the recording industry. These disks range from up 10 cm up to 30 cm in diameter, are made of aluminium and are read by laser. Optical disks are either CD ROM which are read-only disks, or   CD R/RW which can also be written to. They can store information in the form of pictures and sound taken with a TV camera and  microphone. Pictures are stored as single frames on the disk surface but   are read in sequence to give the effect of a moving picture by enabling the workings of the computer to be combined with television style pictures and sound. An   example of their use is with computer based training (CBT).

23      Optical cards are approximately the size of a credit card and can hold over two million bytes of information. They can be used to store large amounts of personal information such as medical records and employment history.

Can you think of any systems that would benefit from using an optical disk or card? Make a list of four different uses.

Input devices

24   We have just considered some of the many ways of inputting information into the CPU. This information is, however, of a static nature. Often a computer system will need more dynamic information-information that changes in time-and to cater for this, other devices are available. Devices may vary in sophisication according to the types of application for which they are being used. The following devices are used for inputting information.

·  Keyboards

·  The mouse and trackball

·  Games paddles and joysticks

·  Optical and magnetic readers

·  Plotters

·  Touch screens

·  Speech recognition