IT and Applications

A computer is an electronic, programmable machine that accepts raw data as input, processes it according to stored instructions, and produces meaningful information as output. Data is the raw fact entered into the machine, and information is the processed result that a person can use.

Five characteristics explain why computers are useful. Speed means millions of instructions per second. Accuracy means results free from error when the instructions and data are correct. Diligence means the machine works without tiredness or loss of attention. Versatility means the same machine can do very different jobs by running different programs. Storage means large volumes of data and instructions can be kept and recalled quickly.

Digital and analog computers

Digital computers work with discrete binary digits, $0$s and $1$s, and compute with high precision. Analog computers measure continuous physical quantities such as voltage, pressure, or temperature. A calculator and a bank server are digital computers. A traditional speedometer and a bedside ECG monitor are analog instruments.

Five generations of computers

1. First generation (1940 to 1956). Vacuum tubes switched circuits, magnetic drums stored data, and programs were written in machine language. Machines such as ENIAC and UNIVAC I were enormous, hot, and prone to tube failure.
2. Second generation (1956 to 1963). Transistors replaced tubes, magnetic cores stored data, and assembly language plus early high level languages such as FORTRAN and COBOL appeared. Machines became smaller, faster, and far more reliable.
3. Third generation (1964 to 1971). Integrated circuits packed many transistors onto one chip, multiprogramming operating systems arrived, and keyboards and monitors began replacing punched cards. The IBM 360 family is a typical example.
4. Fourth generation (1971 to the present). Microprocessors built with very large scale integration put a whole CPU on one chip, starting with the Intel 4004. Personal computers, laptops, and computer networks spread widely.
5. Fifth generation (the present onward). Research centers on artificial intelligence, parallel processing, and new chip designs, aiming at natural language understanding, voice recognition, and learning systems.

Classifying computers by size

Microcomputers use one microprocessor and serve one person at a time. Desktops, laptops, and smartphones are microcomputers. Minicomputers are mid range machines that serve a department or a small company. Mainframes are large multiprocessor machines that handle thousands of simultaneous transactions, such as core banking systems and airline reservation systems, with high throughput and fault tolerance. Supercomputers are the fastest class, built for massive parallel calculation such as weather forecasting and scientific simulation. The past-question bank records a 3 mark question asking for any two types of computer, so be ready to describe two classes with an example of each.

How data is represented: bits, bytes, and codes

Everything inside a digital computer is stored as bits. Eight bits make a byte, and larger units follow powers of two: $1 \text{ KB} = 2^{10} \text{ bytes} = 1,024 \text{ bytes}$ and $1 \text{ MB} = 2^{20} \text{ bytes} = 1,048,576 \text{ bytes}$. A 256 MB file therefore holds $256 \times 2^{20} = 2^{28} = 268,435,456$ bytes. Note that memory sizes use these binary multiples, while some storage labels round to thousands, so check which base a question uses. Text is represented by agreed codes: ASCII covers basic English characters, and Unicode (usually UTF-8) covers scripts from around the world, including Nepali.

Where computers are used

Businesses use computers for accounting, billing, stock control, and customer records. Banks use them for deposits, clearing, and online services. Schools use them for teaching and records, hospitals for patient data and diagnosis support, and governments for records and citizen services. Science, design, communication, and entertainment complete the picture of an everyday tool.