A computer is an electronic device that accepts data as input, processes it according to a set of instructions, and gives the desired result as output. The word computer is derived from the Latin word "computare", which means to calculate. Over the years, computers have grown from simple calculating machines into powerful devices that can store vast amounts of information, communicate across the globe, control machines, and help us learn, create and entertain. In schools, homes and offices, the computer has become an essential tool for study, work and communication.
A computer cannot do anything on its own. It needs two partners to function: the hardware, which is the physical machinery we can touch, and the software, which is the set of instructions that tells the hardware what to do. Together they form a system that works through a sequence called the input-process-output cycle. This chapter explains what a computer is, how it works, the generations of computers, the basic parts of a computer system, the types of computers, and the important concepts of data and information.
A computer is an electronic machine that works on instructions given to it. It performs four basic operations: it accepts data (input), stores the data and instructions (storage), processes the data (process), and produces the results (output). This working is called the IPOS cycle, where I stands for Input, P for Process, O for Output and S for Storage.
The main features of a computer are speed, accuracy, diligence and versatility. A computer can perform millions of calculations in one second, and it never gets tired of doing the same work again and again. However, a computer has no intelligence of its own; it only follows the instructions given by humans. Its accuracy also depends on the correctness of the data and the program fed into it. If the input is wrong, the output will be wrong, which is expressed by the phrase "Garbage In, Garbage Out" (GIGO).
Data is the raw, unorganised facts and figures that have no meaning on their own. For example, the number 45, the word "Monday" or a list of temperatures are pieces of data. When data is processed and organised so that it becomes meaningful and useful, it is called information. For example, "The temperature on Monday was 45 degrees" is information. The processing may involve calculations, comparisons, sorting or arranging data. A computer converts raw data into useful information through the input-process-output cycle.
Computers have evolved through five generations, each using better technology and becoming faster, smaller and cheaper.
The first generation (1940 to 1956) used vacuum tubes. These computers were huge, consumed a lot of electricity, generated enormous heat and were very slow. ENIAC and UNIVAC were famous first-generation computers.
The second generation (1956 to 1963) replaced vacuum tubes with transistors. Transistors were smaller, faster, cheaper and generated less heat. Second-generation computers used magnetic tapes and disks for storage.
The third generation (1964 to 1971) used integrated circuits (ICs), in which many transistors were packed onto a single silicon chip. These computers were much smaller and more reliable. They supported keyboards and monitors for input and output.
The fourth generation (1971 onwards) used microprocessors, where the entire CPU was placed on a single chip. This generation gave us personal computers (PCs), laptops and the growth of the Internet and graphical user interfaces.
The fifth generation (present and future) focuses on artificial intelligence (AI), which aims to create computers that can learn, reason and think like human beings. These computers use parallel processing, robotics and natural language interfaces.
A computer system is made of four main parts: the CPU, memory, input devices and output devices.
The Central Processing Unit (CPU) is called the brain of the computer. It controls all the operations and performs all the calculations. It has three main parts: the Control Unit (CU), which directs and coordinates all operations; the Arithmetic Logic Unit (ALU), which performs all arithmetic operations (add, subtract, multiply, divide) and logical operations (comparisons); and the registers, which are small, fast memory locations inside the CPU.
Memory is used to store data and instructions. The primary memory is the memory the CPU can access directly, and it includes RAM (Random Access Memory), which is volatile and loses its contents when power is off, and ROM (Read Only Memory), which is non-volatile and permanently stores instructions needed to start the computer. The secondary memory is the permanent storage such as a hard disk, which stores data even when the computer is switched off.
Input devices send data to the computer, such as the keyboard, mouse, scanner, microphone and webcam. Output devices display or print the results, such as the monitor, printer and speaker.
Computers can be classified according to their size and power. Supercomputers are the fastest and most powerful computers, used for weather forecasting, scientific research and complex calculations. Mainframe computers are large and powerful systems used by organisations like banks and airlines to process large amounts of data. Mini computers are smaller than mainframes and were used by smaller organisations. Microcomputers or personal computers (PCs) are the computers we use at home and school. These include desktops, which stay on a desk, and portable computers such as laptops, notebooks and tablets. Smartphones are also small computers that fit in our pocket.
Memory is measured in units. The smallest unit is the bit, which holds either a 0 or a 1. Eight bits make one byte, which can store one character. Larger units are kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB) and petabyte (PB). One kilobyte is equal to 1024 bytes, one megabyte is equal to 1024 kilobytes, and so on. To understand the capacity, a typical photo may take about 2 to 5 MB, a movie about 1 to 2 GB, and a modern hard disk can store 1 TB or more.
| Generation | Technology Used | Main Feature |
|---|---|---|
| First (1940-1956) | Vacuum tubes | Huge, slow, generated heat |
| Second (1956-1963) | Transistors | Smaller, faster, cheaper |
| Third (1964-1971) | Integrated circuits (ICs) | Smaller and more reliable |
| Fourth (1971 onwards) | Microprocessors | Personal computers introduced |
| Fifth (present) | Artificial intelligence | Learning and reasoning computers |
| Unit | Size in relation |
|---|---|
| Bit | 0 or 1 |
| Byte | 8 bits |
| Kilobyte (KB) | 1024 bytes |
| Megabyte (MB) | 1024 KB |
| Gigabyte (GB) | 1024 MB |
| Terabyte (TB) | 1024 GB |
A computer is an electronic machine that follows the input-process-output cycle to turn raw data into useful information. It has evolved through five generations, from vacuum tubes to artificial intelligence, becoming smaller, faster and cheaper at every step. A computer system is made up of the CPU, memory, input devices and output devices, and its capacity is measured in units from bits to terabytes. Understanding these fundamentals is the foundation for learning about hardware, software and the many applications of computers, which are covered in the chapters that follow.