Lesson 2: Computer Components
Objectives
At the end of this lesson, you will understand:
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Skills You Will Need
Before you learn the stated objectives, you should be familiar with:
- What a computer is
- The various types of computers
- The various uses of a computer
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Session 1: Parts of a PC
A computer has various parts and each part performs a specific function. You will learn about some of the important parts of computers and their functions. Some important parts of the computer are shown in Figure 2.1.
1. | System Unit |
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2. | Monitor |
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3. | Printer |
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4. | Keyboard |
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5. | Mouse |
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Figure 2.1: Parts of a computer
A system unit consists of various internal parts, such as motherboard, video card, and sound card. Typical external components attached to a computer include monitor, keyboard, mouse, and printer.
Note The parts of the computer that you can touch and feel are collectively called hardware.
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Connecting the PC
The following points will help you understand how the computer parts are connected to each other by cables.
- The system unit is connected to the power supply.
- The monitor is connected to the system unit and to the power supply.
- The keyboard is connected to the system unit.
- The mouse is connected to the system unit.
- The printer is connected to the system unit and to the power supply.
- Other hardware devices, such as scanners and speakers are connected to the system unit and to the power supply.
Figure 2.2 helps you to understand the connectivity of the parts of a PC.
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Items that connect to the power switch |
Items that connect to the system unit |
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Figure 2.2: Connecting the PC. 1, 2, and 3 represent the connectivity to the system unit. A, B, C, and D represent the connectivity to the power switch.
Session 2: The Input-Process-Output Cycle
Any activity, whether simple or complex, follows the basic principle of Input-Process-Output (I-P-O). For example, consider the simple task of making tea. (See Figure 2.3.) This task requires tea leaves, water, sugar, and milk as the input. The process includes boiling water, brewing tea leaves, straining, and adding milk and sugar. The hot cup of tea that results at the end of the process is the output.

Figure 2.3: The I-P-O cycle for making tea
Computers also work on the Input-Process-Output principle. (See Figure 2.4.) Input refers to the data and instructions given to the computer. Process refers to what the computer does with the data. Output refers to the result of the process.
For example, you want the computer to do a simple calculation: the multiplication of two numbers, 56 and 45. You must first provide the input and specify the process. Here, the numbers 56 and 45 are the input and multiplication is the process. The computer performs the multiplication process on the given inputs. This process results in 2520 as the output.
Figure 2.4: The I-P-O Principle
Check Your Learning
Identify a task. List the input, process, and output for the chosen task in the space provided. Remember, just as there can be multiple inputs required for a task, there can be multiple outputs resulting from a process.
Task description
Input(s)
Process
Output
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Session 3: Input Devices
In the Input-Process-Output cycle, input for the process is provided through a device. Devices used to provide data and instructions to the computer are called input devices.
Some important computer input devices are listed below:
- Mouse
- Keyboard
- Scanner
- Microphone
- Web camera
Mouse
A mouse is used to point to and select options displayed on the monitor. It is usually connected to the system unit with a long wire, although wireless mouse devices are also increasingly available. When the user moves a standard mouse, the mouse ball (a rubber ball on the underside that rolls in all directions) activates sensors that move the screen pointer in the same direction.
A mouse may have two or three buttons. The primary button (usually the left button) is the most frequently used button. Newer mouse devices called scroll mouse or wheel mouse come with a wheel between the left and right buttons. (See Figure 2.5.) This wheel enables you to smoothly scroll through screens of information. Optical mouse is another advanced pointing device that uses a light-emitting component instead of the mouse ball. It detects movement by sensing changes in the light reflected by its light-emitting component.

Figure 2.5: Scroll mouse
When you move the mouse on a flat surface, you will see an arrow moving on the screen correspondingly. This arrow is known as the mouse pointer. (See Figure 2.6.)

Figure 2.6: Mouse pointer
It is good practice to use a mouse pad instead of just any flat surface. A mouse pad is a small mat with a plastic surface and a rubber or plastic-based cushion on which you can move the mouse. It provides greater traction than smooth surfaces and this makes it easier to move the mouse pointer with greater precision. The mouse ball is likely to glide and not roll on smooth glass or wooden surfaces.
Keyboard
The keyboard (see Figure 2.7) is used for typing text into the computer. A computer keyboard is similar to that of a typewriter, but it has additional keys as well. The most commonly available computer keyboard has 104 keys.

Figure 2.7: Keyboard
Several different types of keys are available on the keyboard. The keys are categorized as:
- Alphanumeric keys: These keys include letters and numbers.
- Punctuation keys: These keys include the colon (:), the semicolon (;), the question mark (?), single quotes ('), and double quotes (").
- Special keys: These keys include such as Arrow keys, Control keys, and Function keys (F1 to F12). These keys perform different actions depending on where they are used. For example, the ENTER key starts a new paragraph in a Word processor, but starts the Search process after a user has entered Search text in a search engine.
Function keys are special keys that are used to perform specific tasks. They are labelled as F1, F2, F3, and so on, up to F12. The functionality of the keys differs from program to program. Typically, the function of the F5 key is to refresh the data showing on your monitor screen.
Software refers to computer instructions or data that can be stored electronically.
The insertion point (see Figure 2.8) is the blinking line that indicates the position on the screen where the text will appear as it is being typed.
Figure 2.8: Text document with insertion point
Scanner
A scanner (see Figure 2.9) is used to make an exact digital copy of a picture or a photograph. For example, if you are creating a family newsletter, you can use a scanner to reproduce photographs and insert them into the report.

Figure 2.9: Scanner
Microphone
A microphone (see Figure 2.10) is a device used to digitally record sound. Microphones convert sound waves into audio signals.

Figure 2.10: Microphone
Web Camera
A Web camera (see Figure 2.11) is a device capable of converting visual images into digital form. When connected to a computer, it functions as the eye of the computer. You can use it to take a photograph of yourself and store it in the computer or for video conferencing.

Figure 2.11: Web camera
Check Your Learning
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Identify and list the input device(s) for the task that you described in Activity 2.2.1.
- Using the Notepad program in Windows is one way you can type text using your computer. It is used as one would use an ordinary paper notepad. Type a paragraph about your family in Notepad.
- To start Notepad, click Start, point to All Programs, point to Accessories, and then click Notepad.
Observe the movement of the insertion point as you type.
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Session 4: Output Devices
Output devices transfer data out of the computer in the form of text, images, sounds, and so on.
There are three important output devices connected to the system unit:
Monitor
A monitor (see Figure 2.12) resembles a television screen, only with a much higher resolution for better display quality. It is used to display information from the computer. The monitor displays text and graphics. It typically comes with its own separate power button to turn it on or off.

Figure 2.12: Monitor
Printer
A printer is used to transfer data from a computer onto paper. Both color printers and greyscale printers are available on the market. The different types of printers are dot matrix printers, inkjet printers, and laser printers. (See Figure 2.13.)

Figure 2.13: Dot matrix printer, inkjet printer and laser printer
The differences between the three types of printers are listed in Table 2.1.
Table 2.1: Differences between Dot Matrix Printer, Inkjet Printer and Laser Printer
Dot matrix Printer |
Inkjet Printer |
Laser Printer |
Prints characters in the form of dots |
Prints fully formed characters |
Prints fully formed characters |
Speed is measured in terms of characters per second |
Speed is measured in terms of pages per minute |
Speed is measured in terms of pages per minute |
Speed ranges from 200 to 540 characters per second |
Speed ranges from 4 to 8 pages per minute |
Speed ranges from 4 to 20 pages per minute |
Speakers
Speakers (see Figure 2.14) are used to play sound. They may be built in or externally connected to your system. Speakers allow you to listen to music and hear sound effects and spoken text using your computer. Suppose you want to give a presentation to a group of visually impaired people and use a multimedia format. To make the information more accessible to your audience, you can structure the lesson around an audio component. This allows the attendees to more fully engage with your material by using sound rather than relying solely on the usual screen presentation.

Figure 2.14: Speakers
Session 5: Input/Output Devices
Some devices perform the activities of an input device and those of an output device. Such devices are called input/output devices or I/O devices. Modems and network interface cards are examples of input/output devices.
Modem
Data can be transmitted over different media, such as telephone cables and radio signals. Telephone cables can carry only waveforms called analog signals. Analog signals are prone to disturbances from noise and magnetic pulses.
Digital signals are a relatively new form of transmission that use binary format (an encoding/decoding system based on 0s and 1s) to send and receive data. This is the same format used by computers to send and receive data. However, digital signals cannot be sent through telephone lines. Therefore, the digital signals must be converted to analog signals before they can be transmitted through telephone cables. Similarly, the transmitted data has to be converted to digital signals at the receiving end. A modem (see Figure 2.15) converts the digital signals to analog signals and vice versa.
When you send a message from your computer to another computer, the modem acts as an output device. However, when your computer receives a message, the modem acts as an input device. A modem can be external or internal to the system unit. Modems that are connected to the system unit through cables are called external modems.

Figure 2.15: Modem
Modems are also available as part of the computer system unit. Modems that are built-in to the system unit are called internal modems.
Network Interface Card
A network interface card is a card that is installed in a computer so that it can be connected to a network. (See Figure 2.16.) Network interface cards provide a dedicated, full-time connection to other computers. Most network interface cards are designed for a particular type of network, although some can serve multiple networks. The most typical network is, Ethernet, which is a network standard of computer communication using either coaxial or twisted pair cable.

Figure 2.16: Network interface card
Note A computer network is a collection of interconnected computers that can share resources and data.
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Check Your Learning
- Which of the following are input devices, output devices or input/output devices?
- Television screen
- Display board at railway stations
- Stereo system
- Speakers
- Microphone
- Telephone
- Fax machine
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Session 6: System Unit
When you have a conversation with a friend, your ear acts as the input device. It receives the information your friend gives you and passes on the information to your brain. Your brain acts as the processing device. It understands the information and frames an appropriate response. The mouth acts as the output device and gives a reply to your friend.
On a computer, the keyboard and mouse are input devices. The box-like structure, called the system unit, is responsible for all the processing required to convert the input to the required output.
The monitor and printer are output devices. These input and output devices attached to your computer need to connect to a component within your system unit to allow data to flow. For example, the monitor is connected to a video card and the speakers to a sound card. The video card and the sound card, in turn, reside on the motherboard together with the processor, memory, and optional internal I/O devices, such as a network interface card. Today, the connections are usually clearly marked and color-coordinated on the back of the computer so it is clear where each device needs to be attached.
Motherboard
The system unit contains a large board that has a number of tiny electronic circuits and other components. It is known as the motherboard. The motherboard is a very important part of the system unit and houses several vital components of the computer.
The microprocessor is the most important component of the motherboard. Data is received from the input devices. The actual processing of data the arithmetic or logical operations on the given data occurs in the microprocessor. Finally, the processed information is sent to the output devices. Figure 2.17 depicts the working of a computer.
Figure 2.17: Working of a computer
Video Card
A video card (see Figure 2.18) plugs into a personal computer and gives it display capabilities. In other words, it enables your computer to represent data in a visual form. Video cards are also called video adapters, video boards, video display boards, graphics cards, and graphics adapters. Each adapter provides digital-to-analog conversion, video RAM, and a video controller so that data can be sent to a computer's display. If you are purchasing a new computer and specific tasks you want to perform with the computer (such as Internet video games), it is worth researching what type of video card will work best for your program.

Figure 2.18: Video card
Sound Card
A sound card (see Figure 2.19) is a device in the system unit that enables a computer to accept, process, and play sound. A sound card enables the computer to record sound through a microphone, manipulate sound stored on a disk, and output the sound through speakers. If you plan to record or listen to music, researching sound card capabilities before buying a new computer can increase your satisfaction with your new system.

Figure 2.19: Sound card
Check Your Learning
Table 2.2 lists the various parts of a computer and a group of corresponding real-life objects in a jumbled order. Match the parts of the computer with the corresponding objects.
Table 2.2: Comparing Parts of a Computer with Corresponding Objects
Parts of a computer | Similar objects |
Monitor | Typewriter |
Keyboard | Pointing device |
Mouse | Television screen |
System Unit | Photocopier |
Printer | Box |
Table 2.3 lists various processes and processing devices. Match each process with the appropriate processing device.
Table 2.3: Identifying the Processing Device
Process | Processing device |
Stitching a cloth | The human brain |
Cooking rice | Juicer |
Thinking | Grinder |
Grinding flour | Sewing machine |
Making fruit juice | Cooker |
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Test Your Knowledge
- Which one of the following statements is true about a dot matrix printer?
- It can print 200-740 characters per second.
- Its speed is measured in terms of characters per second.
- It prints fully formed characters.
- Special keys on the computer keyboard do not include:
- Control keys
- Function keys
- Alphanumeric keys
- Two teenagers are playing a video racing game. They have to drive the car so that it moves in all directions - left, right, forward and backward. Identify the easiest way to play the game.
- Using the arrow keys
- Using the mouse
- Using the function keys
- Statement A: A microprocessor performs the actual processing of data in the system unit.
Statement B: A motherboard is a part of the microprocessor.
- Both statements are true.
- Statement A is true and Statement B is false.
- Statement A is false and Statement B is true.
- Statement A: A modem can be external or internal to the system unit.
Statement B: A modem is an input device.
- Both statements are true.
- Statement A is true and Statement B is false.
- Statement A is false and Statement B is true.
Lesson Objective Checklist
Skills Acquired | Yes | No |
I can identify the different parts of a personal computer. |  |  |
I understand the connectivity of the parts of a PC. |  |  |
I can explain the Input-Process-Output cycle. |  |  |
I can distinguish between input, output and input/output devices. |  |  |
I can identify the function of the processing devices. |  |  |
Terms to Remember
- Hardware refers collectively to the parts of a computer that you can touch and feel.
- Input refers to data and instructions given to the computer.
- Input devices are used to provide data and instructions to the computer.
- Input/output devices perform the activities of an input device in addition to those of an output device.
- The Insertion point is the blinking line that indicates the position on the screen where the text will appear as it is being typed.
- A Keyboard is used for typing text into the computer.
- A Microphone is a device used to record sound. Microphones convert sound waves into audio signals.
- The Microprocessor is the most important component of the motherboard that performs the actual processing of data the arithmetic or logical operations on the given data.
- A Modem is an electronic device that converts digital signals to analog signals and vice versa.
- A Monitor is used to display information from the computer.
- The Motherboard is a large board contained in the CPU that has a number of tiny electronic circuits and other components. It houses several vital components of the computer.
- A Mouse is used to point to and select options displayed on the monitor.
- A Mouse pad is a small mat with a plastic surface and a rubber or plastic-based cushion on which you can move a mouse.
- The Mouse pointer is an arrow that moves on the screen to correspond to the movement of the mouse.
- Network interface card is a card that is installed in a computer so that it can be connected to a network.
- An Optical mouse is an advanced pointing device that uses a light-emitting component instead of the mouse ball. It detects movement by sensing changes in the light reflected by the light-emitting component.
- Output refers to the result produced by a computer when it has processed data.
- Output devices are devices that are capable of representing information on a computer.
- Printers are used to transfer data from a computer onto paper.
- Process refers to what the computer does with the information it receives.
- A Scanner is used to make an exact digital copy of a picture or a photograph, which can be stored on a computer.
- Scroll mouse or wheel mouse comes with a wheel between the left and right buttons. The wheel enables you to smoothly scroll through screens of information.
- A Sound card is a device in the CPU that enables a computer to accept, process, and play sound.
- Speakers allow you to listen to music and hear sound effects and spoken text, using your computer.
- The system unit is the main body of a computer, which holds the processing devices required to convert input into output. These processing devices include the motherboard, internal disk drives, and other system hardware, such as video cards and sound cards.
- A Video card plugs into a personal computer to give it display capabilities.
- A Web camera is a device capable of converting visuals into digital form.
©2004 Microsoft Corporation. All rights reserved.
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