1. Chapter 2: Computer System Components
Computer Skills-1
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Chapter 2: Computer System Components
Department of Computer Science
Foundation Year Program
Umm Alqura University, Makkah

2. The Objectives and the outcomes
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

3. 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.

4. 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

5. 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)

6. 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.

7. 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.
Function of logic section is to perform logic operations such as comparing, selecting, matching and merging of data.

8. 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

9. 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

10. 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

11. 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.

12. 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.

13. 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

14. 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

15. 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.

16. 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.

17. How Computers Store Data
Think of a byte as eight switches

18. 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.

19. 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.

20. 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.

21. Software System software Application software System 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:

22. 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

23. 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

24. 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
programs
Web browsers
Game programs

25. 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

26. 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.

27. Output Unit Monitor Speakers
Printer (Impact, Dot Matrix, Non- Impact, Ink Jet, Laser)
Plotters

28. 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.

29. 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

30. Removable Media Devices:
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

31. Other Peripherals Text input devices Keyboard Pointing devices
Gaming devices Joystick
Image/video input devices Image scanner
Audio input devices Microphone