OVERVIEW OF COMPUTER SYSTEM
These devices are examples of computer hardware. A computer system
needs to have these hardware to function.
COMPUTER SYSTEM
A computer system is defined as combination of components designed to
process data and store files.
A computer system consists of four major hardware components; input
devices, output devices, processor and storage devices.
A computer system requires hardware, software and a user to fully function.
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Software refers to set of instructions that tell the hardware what to do.
Software can also have various other functions such as performing
computation, communication with other software and human interaction.
User refers to a person who uses the computer for any purposes such as
work, business and entertainment.

COMPUTER HARDWARE
Computer hardware consists of:
§ input devices
§ processor
§ output devices
§ storage devices
Input Devices
Input devices feed data or commands in a form that the computer can use.
Example of input devices are:
§ Keyboard
§ Light Pen
§ Joystick
§ Microphone
§ Mouse
§ Video
§ Digital camera.
Processor
The CPU is an example of a processor. It has the
same important as the brain to human being.
Output Devices
Output devices such as the monitor shows
people the process data or information. This
type of information can be understood and use
by computer user. Other example of output
devices are:
§ Printer
§ Plotter
§ Speaker
Storage Devices
Storage usually means secondary storage. It
consists secondary storage devices such as
hardisk, Floppy Disk, diskette, CD ROM and DVD
ROM.
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COMPUTER SOFTWARE
There a 2 types of computer software, system software and application
software. System software is any computer software that helps to run
computer system. System software controls, integrate and manages the
individual component of a computer system.
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LESSON 2
INTRODUCTION TO COMPUTER SYSTEM
COMPUTER HARDWARE BLOCK DIAGRAM
An Input device feed raw data to the processor. A processor processes raw
data and turns it into useful information. A storage device keeps or stores
both process and unprocess data for later usage. An output device shows or
display the processed data.
INPUT DEVICES
When data is entered into the computer system, it is called an input. Input
comes in various forms; texts, graphics, audio and video. Input devices are
needed to input data into the computer system.
Keyboard, mouse, scanner, barcode reader and digital camera are some
example of input devices.
OUTPUT DEVICES
Output is the result of raw input data that has been
processed by the central processing unit into
meaningful information. Common forms of output
are texts, numbers, graphics, sounds, animations
and videos.The most common output devices are
computer screens, speakers and printers.
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STORAGE DEVICES
The system’s primary storage, Random Access Memory (RAM) can only hold
data temporarily. Thus, secondary storage is needed to provide additional
storage. The data stored in the secondary storage is considered permanent
until it is deleted or removed.
Secondary storage can be magnetic disks and optical disks. Examples of
secondary storage are hard disks, rewritable CDs and DVDs as well as
removable disks such as pen drives.
PERIPHERAL DEVICES
External hardware devices attached to the
computer are called peripheral equipments.
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LESSON 3
INFORMATION PROCESSING CYCLE
Do you know how a computer works? We use the computer in our everyday
lives but not all of us know how this machine operates.
Human uses the brain to think, make decisions and process information. A
computer has a brain too, and the brain of a computer is the processor or
the central processing unit (CPU) that processes information.
THE CENTRAL PROCESSING UNIT
The central processing unit or the CPU is the brain of the computer.
All processing activities are done in the CPU. It
utilises the computer memory to execute instructions
from the application software and accomplish a task.
For example: editing a letter, drawing a picture and
sorting numbers.
The processor must be connected to input devices, output devices and
storage devices to carry out the above mentioned tasks.
THE INFORMATION PROCESSING CYCLE
User will input the data to be processed by the processor.
The storage holds databases, files and programs. The output devices
present the processed data as useful information products for the user.
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INPUT
Input is any data or instructions that we enter into the computer system for
processing.
There are some common ways of feeding input data
into the system, which are:
• typing on a keyboard
• pointing with a mouse
CPU accepts instruction from the user and translates the instruction into
readable information (decode).
PROCESS
The processing unit controls all activities within the system. For every
instruction, the control unit repeats a set of four basic operations called the
machine cycle:
Fetching
the process of obtaining a program instructions or data item from memory.
Decoding
the process of translating a program instruction into signals that the
computer can execute.
Executing
the process of implementing the instructions in a program.
Storing
the process of writing the result to the storage or memory.
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STORAGE
Storage is a location which data, instruction and
information are held for future use. Every computer
uses storage to hold system software and application
software.
When we issue a command to start the application
software, the operating system locates the program in
storage and loads it into memory.
A storage medium, also called secondary storage is the physical material in
the computer that keeps data, instruction and information.
A storage device is the computer hardware that records or retrieves items to
and from storage media.
OUTPUT
Output is data that has been processed into a useful
form, called information. There are four types of
output, which are texts, graphics, audio and video.