Chapter 2: Computer System Components

Computer Skills-1

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Department of Computer ScienceFoundation Year ProgramUmm Alqura University, Makkah

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The Objectives and the outcomes

Objectives:• To understand hardware and software• To understand how information is stored in the computer• To understand different types of software• To understand different devices like Input, CPU, Output and

motherboard etc.

Outcomes:• Students would be able to understand different components of

computers• Students would be able to understand an idea of 0 and 1• Students would be able to understand software categories• Students would be able to understand the detail structure of

computer

Computer System Components

Computer system components can mainly be divided into two

main parts, namely; hardware and software.

Hardware:

• Hardware is the electronic and mechanical parts of the

computer.

• Figure 1 represents the general block diagram for the hardware

parts of a digital computer.

Computer System Components

Typical computer system consists of the following major

components:

• The central processing unit (CPU)

• Main memory

• Secondary storage devices

• Input devices

• Output devices

Fig 1. Block Diagram of Computer

CPU - Central Processing Unit

CPU consists of the following features:

• CPU is considered as the brain of the computer

• CPU performs all types of data processing operations

• It stores data, intermediate results and instructions(program)

• It controls the operation of all parts of computer

CPU itself has the following two components.

• Control Unit

• ALU (Arithmetic Logic Unit)

CPU - Central Processing Unit

Control Unit

This unit controls the operations of all parts of computer but does not carry out any actual data processing operations.

Functions of this unit are:

• It is responsible for controlling the transfer of data and instructions among other units of a computer.

• It manages and coordinates all the units of the computer.

• It obtains the instructions from the memory, interprets them, and directs the operation of the computer.

• It communicates with Input/Output devices for transfer of data or results from storage.

• It does not process or store data.

CPU - Central Processing Unit

ALU(Arithmetic Logic Unit)

This unit consists of two subsections namely

• Arithmetic section

• Logic Section

Arithmetic Section

• Function of arithmetic section is to perform arithmetic operations like addition, subtraction, multiplication and division. All complex operations are done by making repetitive use of above operations.

Logic Section

• Function of logic section is to perform logic operations such as comparing, selecting, matching and merging of data.

CPU - Central Processing Unit

Registers:

In a computer, a register is one of a small set of data holding places that are part of a computer processor. For example;

• Data Registers

• Address Registers

• Status Registers

• Program Counter

• General purpose Registers

Memory or Storage Unit

Computer memory is any physical device capable of storing information temporarily or permanently.

Memory is primarily of three types:

• Cache Memory

• Primary Memory/Main Memory

• Secondary Memory

Primary Memory or Main Memory

• This unit can store instructions, data and intermediate results. This unit supplies information to the other units of the computer when needed.

• It is also known as internal storage unit or main memory or primary storage or Random access memory(RAM)

• Its size affects speed, power and capability.

Functions of main memory are:

• It stores all the data and the instructions required for processing

• It stores intermediate results of processing

• It stores final results of processing before these results are released to an output device

• All inputs and outputs are transmitted through main memory

Primary Memory or Main Memory

Main memory is divided into two parts:

• RAM (Random Access Memory)

• ROM (Read Only Memory)

Random Access Memory (RAM) : The data stored in RAM is lost

forever when the power is turned off.

Read Only Memory (ROM): The instructions in ROM are set by

the manufacturer and cannot be changed by the user.

Secondary Memory

• This type of memory is also known as external memory or non-volatile

• It is slower than main memory.

• These are used for storing data/Information permanently.

Characteristic of Secondary Memory are:

• These are magnetic and optical memories

• It is known as backup memory.

• It is non-volatile memory.

• Data is permanently stored even if power is switched off.

• It is used for storage of data in a computer.

• Computer may run without secondary memory

• Slower than primary memories.

For Example; Hard disk, Floppy disk, Tape drive, CD-ROM, Flash Memory and others.

Cache Memory

Cache memory is a very high speed semiconductor memory which can

speed up CPU. It acts as a buffer between the CPU and main memory.

The advantages of cache memory are as follows:

• Cache memory is faster than main memory.

• It consumes less access time as compared to main memory.

• It stores the program that can be executed within a short period of time.

• It stores data for temporary use.

The disadvantages of cache memory are as follows:

• Cache memory has limited capacity

• It is very expensive

Other kinds of Memory:

PROM: Programmable Read Only Memory

EPROM: Erasable Programmable Read Only Memory

Cache Memory

Registers: These are not a part of the main memory

How Computer Stores Data

• All data that is stored in a computer is converted to sequences of 0s and 1s.

• A computer’s memory is divided into tiny storage locations known as bytes.

• One byte is only enough memory to store a letter of the alphabet or a small number.

• Most computers today have millions, or even billions, of bytes of memory.

How Computers Store Data

• Each byte is divided into eight smaller storage locations known as

bits. The term bit stands for binary digit.

• Computer scientists usually think of bits as tiny switches that can

be either on or off.

• In most computer systems, bits are tiny electrical components that

can hold either a positive or a negative charge.

• Computer scientists think of a positive charge as a switch in the on

position, and a negative charge as a switch in the off position.

How Computers Store Data

• Think of a byte as eight switches

How Computers Store Data

• For example, the pattern shown on the left in Figure shows how

the number 77 would be stored in a byte, and the pattern on the

right shows how the letter A would be stored in a byte.

Storing Numbers

• In computer systems, a bit that is turned off represents the number

0 and a bit that is turned on represents the number 1.

• This corresponds perfectly to the binary numbering system.

• In the binary numbering system (or binary, as it is usually called)

all numeric values are written as sequences of 0s and 1s.

Units of memory storage

• Bit is the smallest unit of storage. The storage capacity of any secondary storage devices is evaluated by the amount of data stored in them.

Software

There are two general categories of software:

• System software

• Application software

System Software

The programs that control and manage the basic operations of a computer are generally referred to as system software. System software typically includes the following types of programs:

System Software

Operating System

An operating system is the most fundamental set of programs on a computer. The operating system:

• controls the internal operations of the computer’s hardware

• manages all of the devices connected to the computer

• allows data to be saved to and retrieved from storage devices allows other programs to run on the computer.

Examples:

• Windows or Linux

for personal computers

• Mac OS - for Macs

• Unix - for mainframes

• Symbian, Android - for mobile phones

System Software

Utility Programs: It is program that performs a specialized task that enhances the computer’s operation or safeguards data.

Examples: virus scanners, file compression programs, and data backup programs.

 

Software Development Tools: They are programs that programmers use to create, modify, and test software.

Examples: Assemblers, compilers, and interpreters

Application Software

• Application software are programs that make a computer useful for everyday tasks.

• These are the programs that people normally spend most of their time running on their computers.

Examples:

• Microsoft Word

• Word processing program

• Adobe Photoshop

• An image editing program

• Spreadsheet programs

• Email programs

• Web browsers

• Game programs

Application Software

General purpose Software

Application software is any software used for specified applications such as:

• Word Processing

• Spreadsheet

• Database

• Presentation Graphics

• Communication

• Tutorials

• Entertainment, Games

Application Software

Special purpose Software

• Special purpose application software is a type

of software created to execute one specific task. For example a

camera application on your phone will only allow you to take

and share pictures. Another example would be a chess game, it

would only allow you to play chess.

Output Unit

• Monitor

• Speakers

• Printer (Impact, Dot Matrix, Non- Impact, Ink Jet, Laser)

• Plotters

Elements of Computer System

• Mouse: Mouse is used for system operation and navigation.

• Keyboard: Keyboard is used to input data in to the system so that the system gives output to the user

• Monitor: Monitor, which again is a very essential part of the computer system, displays the actions that the computer performs on our command.

• Motherboard: Motherboard again a necessary element of the computer system that contains different elements as memory, processor, modem, slots for graphic cards and LAN card.

• Hard Disk: Hard disk is used to store data permanently on computer.

Elements of Computer System

• Speakers: Speakers are also included in basic elements of a computer. It is not an essential element in a computer

• Sound Card: This device enables the computer to output sound to audio devices, as well as accept input from a microphone

• Modem: Modem is used to make a connection with the Internet. Two types of modems are widely used, namely; software modems and hardware modems

• CD (compact disc)

• DVD (digital versatile disc)

• DVD-RAM Drive

• Blu-ray Disc

• BD-ROM Drive

• BD Writer

• HD DVD

• Floppy disk

• Iomega Zip drive

• USB flash drive

• Tape drive

Removable Media Devices:

Other Peripherals

• Text input devices Keyboard

• Pointing devices

• Gaming devices Joystick

• Image/video input devices Image scanner

• Audio input devices Microphone