Components of a Computer System Chapter-2

Topics to be covered What is information system?1

Input Device2

Output Device3

Processing Device4

Communication Devices5

Information System

A complete information system is made up of five (5) parts:

1. Hardware

2. Software

3. Data

4. Users

5. Procedures

It is a set of instructions that control the working of the computer’s operations.

These instructions are stored as programs.

Hardware The hardware consists of all parts of the Computer that you

can see and touch. These include input, processing and output devices.

Software

Data Data consists of raw facts and figures.

UserA user: is a person who uses the computer with a specific

objective. User inputs data and gets the information User requires.

ProceduresA procedure: is an ordered set of tasks for performing some

action.The rules or guidelines that are followed in the use of

hardware, software and data are procedures.

Computer Hardware The equipment that processes data to create

information is called hardware. Hardware for a microcomputer system

consists of a variety of devices.

These may be divided into four(4) basic

categories:

1. Input/Output,

2. Processing,

3. Storage

4. Communication.

Data Information

Input DevicesInput devices are used to feed data and instructions into the computer.

Output DevicesOutput devices translate the processed information generated by the computer into a form that humans can understand.

Monitor This is also called a Visual Display Unit (VDU). It is used to display both data that is entered and data after it

is processed to the user. It is similar to a TV screen and can display text and graphic

images.

CRT LCD

PrintersSince the output on the monitor cannot be stored

for later reference, a printer is used to obtain a permanent copy of the output.

There are different types of printers based on their features which are as follows:

Capabilities of a Printer1. Resolution: This is a measure of the clarity of images

produced. Printer resolution is measured in “dpi (i.e. dots per inch)”. Higher dpi results in better quality images.

2. Color capability: Printers provide the option to print in gray scale using black ink only or with color.

3. Speed: This is measured in number of pages printed per minute.

4. Memory: This is used to store printing instructions and documents waiting to be printed.

Audio Output Devices These devices translate audio information from the

computer into sounds that people can understand. “Speakers” and “Headphones” are widely used audio-

output devices which are connected to a sound card in the system unit and can be used to play music and communicate information from the computer system to users.

Touchscreen

It is both input and output device.

Processing Devices The CPU is the brain of the computer. Sometimes

referred to simply as the central processor, but more commonly called processor, the CPU is where most calculations take place.

In terms of computing power, the CPU is the most important element of a computer system.

Microprocessor In a microcomputer system, the central processing unit

(CPU) is contained on a single chip called the “Microprocessor”.

The microprocessor is the “brain” of the computer and has two basic components:1. ALU (Arithmetic and Logic Unit)2. CU (Control Unit)

ALU (Arithmetic and Logic Unit) The actual processing of the data and instruction are

performed by Arithmetic Logical Unit. The major operations performed by the ALU are (+,-,*,/)

addition, subtraction, multiplication, division, logic and comparison.

Control Unit (CU)

The control unit determines the sequence in which computer programs and instructions are executed.

Storage DevicesA STORAGE DEVICE :is a device for recording (storing) information (data). This is also referred to as MEMORY.

There are basically 2 types of memory:-1. Primary2. Secondary

Primary Memory Primary storage (or main memory or internal

memory) ,often referred to simply as MEMORY.

It is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there

and executes them as required. There are 2 types of Primary memory :-

1. RAM (Random Access Memory) 2. ROM (Read Only Memory)

Secondary MemorySecondary storage holds data and programs even if

electrical power is not available.The most important types of secondary media are

Magnetic and optical disks.

Major Differences

Primary memory Secondary memory • Fast• Expensive• Low capacity• Connects directly to

the CPU

• Slow• Cheap• Large capacity• Not connected directly to

the processor

Communication DevicesThrough communication devices, a computer can communicate with other computer systems located around the world using the Internet.

The important communication devices are :1. NIC-Adapters2. Routers 3. Hubs4. Switches 5. Gateways 6. Modems7. Networking Cables.

Units of Measurement Used in Computers

Computer memory is measured in bit and byte.

Memory capacity is the number of bytes (characters) a storage medium can hold. You can find storage devices of different capacity for the computers.

What are bit, byte, K.byte, M.byte, G.byte, T.byte?

All computers work on a binary numbering system, i.e. they process data in ones or zeros. Bit – 1 and 0 level of storage is called a bit

(short for binary digit). Byte - 8 bits make 1 byte. A byte is the smallest

unit which can represent a data item or a character.

Likewise, kilobyte (KB), megabyte (MB), gigabyte (GB) and terabyte (TB) all are units to represent higher volumes of data.

Comparison between the Units of measurement

Unit Description

Bit 0 and 1

Byte (B) 1 B = 8 bits

Kilobyte (KB) 1 KB = 1024 B

Megabyte (MB) 1 MB = 1024 KB

Gigabyte (GB) 1 GB = 1024 MB

Terabyte (TB) 1 TB = 1024 GB

Highlight’s Input Device Keyboard, Mouse, Scanner

Output Device Monitor, Printer

Processing Device Control Unit & Arithmetic-Logic Unit

Storage Devices Primary Storage RAM, ROM Secondary Storage hard disks, optical disks

Communication Devices Routers, Hubs, Switches