Concept of Computers – JSS1 Computer Studies Lesson Note (First Term)

What is a computer?

A computer can be defined as an electronic device that accepts data as an input, processes it, stores it, and gives out information as the output.

Behavioural objectives

By the end of the lesson, students should be able to:

• define a computer;
• explain the difference between hardware and software;
• name the parts of the computer system and state what each one does;
• give examples of input devices, output devices and storage devices;
• state the functions of the arithmetic logic unit and the control unit.

What are the parts of a computer system?

A computer is a system of many parts working together. The physical parts, which you can see and touch, are collectively called hardware, while software refers to the instructions, or programs, that tell the hardware what to do.

The parts of the computer system are:

• System unit (CPU)
• Monitor
• Mouse
• Keyboard
• Printer
• Speaker
• Modem

System unit

The system unit is the core of a computer system. It is a rectangular box placed on or underneath your desk. The most important component is the central processing unit (CPU), or microprocessor, which acts as the “brain” of your computer. Another component is random access memory (RAM), which temporarily stores information that the CPU uses while the computer is on. The information stored in RAM is erased when the computer is turned off.

Monitor

A monitor displays information in visual form, using text and graphics. The portion of the monitor that displays the information is called the screen. There are two basic types of monitors: CRT (cathode ray tube) monitors and the newer LCD (liquid crystal display) monitors.

Mouse

A mouse is a small device used to point to and select items on your computer screen. A mouse usually has two buttons: a primary button (usually the left button) and a secondary button. Many mice also have a wheel between the two buttons, which allows you to scroll smoothly through screens of information.

Keyboard

A keyboard is used mainly for typing text into your computer. It has keys for letters and numbers, but it also has special keys:

• The function keys, found on the top row, perform different functions depending on where they are used.
• The numeric keypad: these keys, located on the right side of most keyboards, allow you to enter numbers quickly.
• The navigation keys: these arrow keys allow you to move your position within a document or webpage.

Printer

A printer is a part of a computer system that transfers data from a computer onto paper. It allows you to print e-mails, cards, invitations, announcements, and other materials. The two main types of printers are inkjet printers and laser printers.

Speakers

Speakers are used to play sound. They can be built into the system unit or connected with cables. Speakers allow you to listen to music and hear sound effects from your computer.

Modem

A modem is an internet device that sends and receives computer information over a telephone line or high-speed cable. Modems are sometimes built into the system unit, but higher-speed modems are usually separate components.

What are the components of a computer system?

The main components of a computer system are:

1. Input device
2. Output device
3. Storage device
4. Arithmetic logic unit
5. Control unit

Input device

An input device is used for entering data and programs into the computer system by the user for processing. Input devices are divided into two types:

1. Manual input devices
2. Automatic input devices

Examples of input devices are:

1. keyboard
2. mouse
3. joystick
4. graphics tablet
5. trackball
6. touchpad
7. touch screen
8. microphone
9. sensor
10. scanner
11. webcam

Output device

Output devices are pieces of hardware that send usable processed information out of the computer.

Examples of output devices are:

1. printer
2. monitor
3. touch screen
4. plotter
5. speakers
6. headphones
7. media projector

Storage device

A storage device is used for storing data and instructions before and after processing. Examples are hard disk drives and compact disk drives.

Arithmetic logic unit

The arithmetic logic unit carries out arithmetic operations such as addition, subtraction, multiplication and division. It also carries out logical operations such as greater than, less than and equal to.

Control unit

The control unit controls all operations such as input, processing and output. It takes care of the step by step processing of all operations inside the computer.

Evaluation

1. Define a computer.
2. What is the difference between hardware and software?
3. Name four input devices and four output devices.
4. State the function of the arithmetic logic unit and of the control unit.
5. What happens to the information stored in RAM when the computer is turned off?

Assignment

1. Name the two basic types of monitors and the two main types of printers.
2. Write two sentences each on the mouse, the keyboard and the modem.
3. List three examples of storage devices mentioned in this lesson.