Computer Fundamentals

A computer is an electronic device that accepts input, processes it under stored instructions and produces output, with the ability to store results. Basic cycle: Input → Processing → Output → Storage. The modern design follows the Von Neumann architecture, in which the program and data are stored in the same memory (the stored-program concept).

Characteristics: speed, accuracy, diligence (no fatigue), versatility, storage capacity, no IQ (cannot think on its own), automation.

Memory aids: Vacuum → Transistor → IC → Microprocessor → AI (V-T-I-M-A). Machine language was used in the first generation. COBOL and FORTRAN belong to the second generation. Keyboard and monitor arrived in the third. Microprocessor arrived in the fourth. AI is the fifth. Watch for the period traps: the second generation starts in 1956 and the first runs from 1940 to 1956.

By size and power:

• Supercomputer: fastest and most powerful. Used for weather forecasting, nuclear simulation, space research and genomics. Speed is measured in FLOPS (floating point operations per second). India's PARAM series was developed by C-DAC under Dr Vijay Bhatkar. Other Indian examples are Pratyush (IITM Pune) and Mihir (NCMRWF). Foreign examples are Cray and Fugaku.

• Mainframe: large organisations such as banks, airlines and railways. Supports bulk transaction processing and many simultaneous users. Example: IBM Z series.

• Minicomputer: midsize, between microcomputers and mainframes, multi-user.

• Microcomputer: built around a microprocessor. Desktop, laptop, tablet, smartphone, single-user.

Supercomputer versus mainframe: a supercomputer solves a few extremely complex scientific calculations quickly. A mainframe handles a vast number of transactions reliably. This is a concept question.

By working principle:

• Analog: processes continuous data (temperature, speed, pressure). Example: thermometer, speedometer.

• Digital: processes discrete binary data (0 and 1). Example: PC.

• Hybrid: combines both. Example: ICU patient monitors, which measure analog body signals and display digital readings.

The CPU is the brain of the computer. Parts:

• ALU (Arithmetic Logic Unit): performs arithmetic (add, subtract) and logical (AND, OR, NOT, comparison) operations.

• Control Unit (CU): directs and coordinates all operations, fetches and decodes instructions and controls data flow. It does not process data itself.

• Registers: very small, fastest storage inside the CPU that hold data and instructions being processed. Examples: Program Counter (PC) holds the address of the next instruction, Instruction Register (IR) holds the current instruction, Accumulator holds intermediate results, MAR holds a memory address, MDR holds data read or written.

Instruction cycle: Fetch → Decode → Execute → Store. Clock speed is measured in Hz (MHz, GHz). Other performance factors are the number of cores, cache size and word length. Bus types: data bus, address bus and control bus.

Conversions to remember:

• Decimal to binary: divide repeatedly by 2 and read remainders bottom to top. Example: 10 = 1010.

• Binary to decimal: multiply each bit by powers of 2. Example: 1101 = 8+4+0+1 = 13.

• Binary to octal: group bits in threes from the right. Binary to hex: group in fours.

• Quick values: 1010 = 10, 1111 = 15 = F, 11111111 = 255 = FF, 10000 = 16.

• Computers use binary because electronic circuits have two states (on and off).

Codes: ASCII is 7-bit (128 characters), extended ASCII is 8-bit (256), Unicode supports all world languages (UTF-8 and UTF-16), and BCD and EBCDIC are other codes.

Bit (0 or 1) → Nibble (4 bits) → Byte (8 bits) → KB → MB → GB → TB → PB → EB → ZB → YB. Each step is 1024 times the previous one in the traditional binary convention (1 KB = 1024 bytes). Order from smallest: Bit \< Nibble \< Byte \< KB \< MB \< GB \< TB \< PB. Network speeds are in bits per second (Mbps), and storage is in bytes. A byte stores one character.