Parts of a computer

Most computers consist of electronic central processing unit (CPU) to which are attached different input devices, output devices and storage devices. The CPU and storage devices are normally built inside a system unit which consists of a metal chassis enclosed in a flat desktop or a tower shaped case. A system unit contains an electronic board called the motherboard that holds and connects together the main electronic components. These are shown in the table below.

 

Processor controls the system

(microprocessor) and processes the

Data

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ROM (Read stores the program instructions

Only Memory) the computer needs to start up

 

RAM (Random stores the data being processed

Access Memory)

Cache memory speeds up the processing

 

The motherboard usually has empty electronic connectors, called expansion slots, into which additional electronic boards (sometimes called expansion cards) can be plugged. This allows extra electronic components to be added. For example, more memory can be added by plugging memory boards (e.g. SIMMS) into the memory slots. Sound facilities can be added by plugging a sound card into an expansion slot. This is one way of upgrading a computer. Another way is to replace the motherboard with a newer and better one.

 

The system unit usually also contains a small speaker (or loudspeaker), the power supply, and some storage devices. These often include: a hard disk drive with a fixed disk that can store a very large amount of data; a floppy disk drive (накопительнагибкихмагнитныхдисках)that uses removable floppy disks (diskettes); a CD-ROM or DVD drive that is used for reading CD-ROM or DVD drive disks (particularly in multimedia computers). Some other devices may be included in the system unit but most input and output devices are plugged into the back of the system unit using connectors known as ports.

 

Power is a function of both speed and capacity. The power of a computer depends on the combination of all the components. When buying a computer, you can often choose between different components. In particular you can choose between different processor speeds, amounts of memory, and hard disk sizes. Units of measurement commonly used in computing are shown below.

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Unit Symbol Meaning Measurement

 

Hertz HZ cycles per frequency

Second

 

Byte B space for one capacity

(pronounced character,

i.e. one letter,

 

like bite) number,

punctuation

mark, symbol

or even a space

 

Hertz are measured using the decimal system but bytes are measured using the binary system. The values of the unit prefixes vary in these two systems as shown in the table below.

 

Unit Symbol Decimal System Binary System

Kilo K 103 =1000 2 10 = 1024

Mega M 10 6 = 1000000 2 20=1048576

Giga G 109= 2 30 =

1000000000 1073741824

(MHZ = megahertz, KB = kilobytes, MB =megabytes, GB = gigabytes)