Every computer, whether it is a huge mainframe or a small smartphone, is made up of many physical parts. These physical parts are called hardware. Hardware includes everything that we can see and touch, such as the keyboard we type on, the mouse we click with, the monitor we look at, and the CPU that does the actual work.
In this chapter, we will learn about the different types of hardware. We will understand what input devices are, what output devices are, and how the CPU processes our data. We will also learn about storage devices, where a computer keeps its data and programs. By the end of this chapter, you will be able to identify each part of a computer and explain its function clearly.
Hardware is the physical and tangible part of a computer system. It is made of electronic and mechanical components. Hardware cannot work on its own; it needs software, which is a set of instructions, to perform any task.
Hardware can be divided into four main categories based on the work it does:
A good way to remember hardware is to think of the computer body. Just as our body has eyes, ears, hands, and a brain, a computer has input devices like the brain's senses, output devices like the mouth, and a processing unit like the brain.
Input devices are used to enter data and instructions into a computer. Without input devices, the computer would never know what work to do.
Keyboard: The keyboard is the most common input device. It looks like a typewriter and has letters, numbers, and special keys. We use it to type text and give commands. The keyboard is divided into different groups of keys like alphabetic keys, numeric keys, function keys, and arrow keys.
Mouse: The mouse is a pointing device used to control the pointer on the screen. We move the mouse on a flat surface and the pointer moves on the monitor. We can select items, click buttons, and drag objects with the mouse. A modern mouse may have a scrolling wheel and extra buttons.
Scanner: A scanner is used to copy pictures and documents from paper into the computer as digital images.
Microphone: A microphone is used to enter sound, such as our voice, into the computer. It is used for voice commands, recording, and online meetings.
Joystick: A joystick is a lever-like input device used mainly for playing computer games.
Webcam: A webcam is a small camera that sends live pictures of us into the computer. It is used for video calls.
Light Pen and Touchscreen: A light pen can draw directly on the screen, and a touchscreen lets us give input by touching the screen with our fingers.
Output devices are used to show the results of the processing done by the computer. Without output devices, we would not be able to see or hear what the computer has done.
Monitor: The monitor looks like a television screen and is the most common output device. It displays text, pictures, and videos. The picture on a monitor is made of tiny dots called pixels. The quality of a monitor depends on the number of pixels it can show.
Printer: A printer is used to print text and pictures on paper. There are two main types of printers. Impact printers like the dot-matrix printer strike the paper with pins, while non-impact printers like inkjet and laser printers do not strike the paper. Laser printers print fast and give clear output.
Speaker: Speakers are used to play sound produced by the computer. They are used for music, videos, and games. Headphones are personal speakers worn on the ears.
Projector: A projector displays the computer screen on a large wall or screen, which is very useful in classrooms and meetings.
The CPU, or Central Processing Unit, is called the brain of the computer. It controls all the parts of the computer and does all the processing work. The CPU is a small chip inside the computer that can perform millions of calculations every second.
The CPU has three main parts:
ALU (Arithmetic and Logic Unit): The ALU does all the arithmetic work like addition, subtraction, multiplication, and division. It also does logical work like comparing two numbers to decide which is larger.
CU (Control Unit): The Control Unit controls and coordinates all the parts of the computer. It directs the flow of data and instructions. It does not do the actual calculations; it only tells other parts what to do.
Registers and Cache: The CPU also has small, very fast memory called registers and cache, where it keeps data that is being used right now.
A CPU that is placed on a single chip is called a microprocessor. Modern microprocessors are so small that they fit on a chip no bigger than a fingernail, yet they contain billions of tiny electronic parts.
Storage devices are used to save data, pictures, and programs so that they can be used later. There are two main types of memory in a computer.
Primary memory (main memory): This is the memory directly connected to the CPU. It is fast but loses its data when the power is switched off. RAM (Random Access Memory) is the primary memory where the computer keeps data it is working with right now. ROM (Read Only Memory) is also primary memory; the computer can only read from ROM, and its data stays even when the power is off.
Secondary memory (auxiliary storage): This is permanent storage used to save data for a long time. Data in secondary storage stays even after the power is switched off. Examples include the hard disk, CD, DVD, pen drive, and memory card.
A hard disk is the main storage device inside a computer and can store huge amounts of data. A pen drive is a small portable storage device that connects to the USB port. CDs and DVDs are optical disks that can store data which is read with a laser.
Computer data is stored in units. The smallest unit of data is a bit, which can be either 0 or 1. Eight bits make one byte. A byte can hold one character, like a letter or a digit.
The units of memory in increasing order are:
So a text file with a few pages is a few kilobytes, a song may be a few megabytes, a movie may be a few gigabytes, and a modern hard disk is measured in terabytes.
All hardware works together in a team. When we press a key on the keyboard, the key sends a signal to the CPU. The CPU, with the help of the Control Unit, understands the instruction and processes it. The result is then sent to the output device, which shows it to us.
For example, when we type a letter in a word processor, the keyboard sends the letters to the computer. The CPU processes the letters and sends them to the monitor, where we see the letters on the screen. If we press Print, the CPU sends the letters to the printer, which prints them on paper. The data can also be saved on the hard disk or pen drive for later use.
This cooperation between hardware and software is what makes a computer system useful and powerful.
| Category | Examples | Function |
|---|---|---|
| Input devices | Keyboard, mouse, scanner, microphone | Give data and instructions to the computer |
| Output devices | Monitor, printer, speakers | Show the results of processing |
| Processing devices | CPU (ALU, CU) | Process the data |
| Storage devices | Hard disk, pen drive, CD, DVD | Save data for later use |
| Memory Unit | Size |
|---|---|
| 1 Byte | 8 bits |
| 1 Kilobyte (KB) | 1024 bytes |
| 1 Megabyte (MB) | 1024 KB |
| 1 Gigabyte (GB) | 1024 MB |
| 1 Terabyte (TB) | 1024 GB |
In this chapter, we learned that hardware is the physical part of a computer system. We studied the four categories of hardware: input devices like the keyboard and mouse, output devices like the monitor and printer, processing devices like the CPU, and storage devices like the hard disk and pen drive. We learned that the CPU is the brain of the computer and is made of the ALU, which does the calculations, and the CU, which controls the other parts. We also studied memory units from the smallest bit to the large terabyte, and we saw how all the hardware works together with software to complete any task. Hardware gives a computer its body, and knowing each part helps us understand how a computer truly works.