1. Components of a Computer System
Chapter-2

2. Topics to be covered What is information system? Input Device 1 2 3 4
Output Device 3
Processing Device 4
Communication Devices 5

3. Information System
A complete information system is made up of five (5) parts:
Hardware
Software
Data
Users
Procedures

4. Hardware Software Data
The hardware consists of all parts of the Computer that you can see and touch.
These include input, processing and output devices.
Software
It is a set of instructions that control the working of the computer’s operations.
These instructions are stored as programs.
Data
Data consists of raw facts and figures.

5. User
A user: is a person who uses the computer with a specific objective.
User inputs data and gets the information User requires.
Procedures
A 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.

6. 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:
Input/Output,
Processing,
Storage
Communication.
Data
Information

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

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

9. 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

10. Printers
Since 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:

11. Capabilities of a Printer
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.
Color capability: Printers provide the option to print in gray scale using black ink only or with color.
Speed: This is measured in number of pages printed per minute.
Memory: This is used to store printing instructions and documents waiting to be printed.

12. 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.

13. Touchscreen
It is both input and
output device.

14. 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.

15. 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:
ALU (Arithmetic and Logic Unit)
CU (Control Unit)

16. 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.

17. Storage Devices A storage device :
is a device for recording (storing) information (data). This is also referred to as MEMORY.
There are basically 2 types of memory:-
Primary
Secondary

18. 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 :-
RAM (Random Access Memory)
ROM (Read Only Memory)

19. Secondary Memory
Secondary storage holds data and programs even if electrical power is not available.
The most important types of secondary media are Magnetic and optical disks.

20. 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

21. Communication Devices
Through communication devices, a computer can communicate with other computer systems located around the world using the Internet.
The important communication devices are :
NIC-Adapters
Routers
Hubs
Switches
Gateways
Modems
Networking Cables.

22. 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.

23. 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.

24. Comparison between the Units of measurement
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

25. 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