Information systems take in raw data through various input devices, store the data, process it by performing functions like calculating and sorting, and output the results through devices like screens and printers. A computer is an example of an information system, with a central processing unit that controls data movement and performs arithmetic/logical operations, internal memory, and connections to external storage and input/output devices. The basic components of a desktop computer system include the system unit, screen, keyboard, mouse, and drives for storage media.

1. INFORMATION SYSTEM

2. Information System
 Initially, the computers were developed to perform specific functions
such as a sequence of calculations.
 Today’s computers are important component of the information
system that is capable of performing many tasks including the
function of communication.
 Computer can be described in terms of input, processing, output and
storage.

3. How the Computer System works?
Input
Process
Data Storage
Output

4. Input
 Input is the raw data that is fed into the information system. The data is fed
in via input devices with many different ways.
 Examples of input devices include keyboards, touch sensitive screens and
scanners. These devices make use of human touch, sound, light and
movement.

5. Storage
 Data is stored in an information system so that it can be utilized when
required.
 It can be stored both temporarily, while a program is running, and
permanently so that it can be preserved while the software and hardware is
not in use.

6. Processing
 This is the terms used to describe the way information systems
convert raw data into useful information.
 Processing includes the following functions:
 Storing
 Drawing
 Calculating
 Sorting
 Searching

7. Output
 Output is the visible or audible result of data processing – information that can be
used.
 Output is made available by output devices i.e., screens, printers and speakers.
 Output can be sounds, visual displays and movements.

8. System Unit
 A computer unit is perhaps the most common example of an information
system.
 The various devices that make up the system are called Hardware.
 The computer itself may be a desktop, laptop, notebook, palmtop or PDA
(Personal Digital Assistant).

9. Desktop PCs
 A standard computer system used in an office or school consists of a
number of components – the system unit itself and other hardware
devices that are connected to it. These hardware devices are often
referred to as peripherals.
 The hardware typically supplied with a computer system includes the
system unit itself, a screen, a keyboard, a mouse, hard drive and
CD/DVD drives.

10. Block diagram of a system
Computer
Keyboard
Hard DiskMouse
CD ROM
Printer
Screen

11. Inside the computer
 Any computer contains a CENTRAL PROCESSING UNIT, where all the instructions are carried out.
The Central Processing Unit can be described as the brain of the entire system.
IMMEDIATE ACCESS STORE (IAS)
CONTROL UNIT
ARITHMETIC AND LOGIC UNIT (ALU)
HARD DISK
DVD DRIVE
CD DRIVE
INPUT
DEVICE
OUTPUT
DEVICE
EXTERNAL STORAGE

12. It includes the following:
o The control unit, which contains the timing of operations and
movements of data inside the computer and between the computer
and peripherals.
o The arithmetic and logic unit (ALU), where calculations are
performed and logical operations are made.
o The immediate access store (IAS), which is the built in memory of the
computer system. It is also called the primary or main storage.