Basics of Computers and Generations: Parts, Memory and MCQs

A computer is an electronic machine that accepts data, processes it according to a stored set of instructions and gives back a result. Computer Awareness is a scoring section in SSC, banking and railway papers because the questions are factual and repeat every year. Almost all of them come from four small areas: what the machine does, who built the early machines, which electronic component defines each generation, and how memory and storage are measured. This chapter fixes those four areas.

What a computer does: the IPO cycle

Every computer works on the input-process-output cycle. Raw, unorganised material is called data; the meaningful result after processing is called information. A keyboard, mouse, scanner, joystick, light pen, barcode reader and microphone are input devices. A monitor, printer, plotter and speaker are output devices. A few devices are both input and output, such as a touchscreen, a modem and a hard disk. The saying GIGO, garbage in garbage out, records the most examinable idea about a computer: it has no intelligence of its own and cannot correct wrong input.

The standard list of characteristics is speed, accuracy, diligence, versatility, storage capacity and automation. Diligence means the machine does not tire or lose concentration over a long run. The two standard limitations are the absence of intelligence and the absence of decision-making power without a program.

From the abacus to the microprocessor

The abacus, developed in China, is treated as the earliest counting device. Mechanical calculation begins with Blaise Pascal, who built the Pascaline in 1642, the first mechanical adding machine. Gottfried Wilhelm Leibniz improved it with the stepped reckoner, which could also multiply.

Charles Babbage designed the Difference Engine and then the Analytical Engine, which already had the parts of a modern computer: a store, a mill, input by punched cards and an output unit. He never completed it, but the design earned him the title Father of the Computer. Ada Lovelace, who wrote the method for computing Bernoulli numbers on that machine, is called the first programmer.

The five generations of computers

Generations are named after the main electronic component, and this single table answers most of the questions set from the chapter.

First-generation machines were enormous, consumed heavy power and needed constant cooling; they used punched cards and magnetic drums. The transistor, invented at Bell Laboratories in 1947 by John Bardeen, Walter Brattain and William Shockley, made the second generation smaller and far more reliable. The integrated circuit, first demonstrated by Jack Kilby in 1958, packed many components on one chip and defines the third generation, which also brought the keyboard, the monitor and the operating system. The fourth generation begins with the microprocessor: Intel released the Intel 4004, the first commercial microprocessor, in 1971, and the personal computer followed. The fifth generation is described by ultra large scale integration, parallel processing and artificial intelligence.

Inside the machine: CPU, memory and storage

The Central Processing Unit is called the brain of the computer. It has three parts. The Arithmetic Logic Unit performs all calculations and comparisons. The Control Unit fetches and decodes instructions and directs the other units, but performs no arithmetic itself. Registers are the smallest and fastest storage locations, sitting inside the processor.

Memory is divided into primary and secondary. Primary memory is RAM and ROM. RAM is read-write and volatile, so its contents vanish when power is cut; its two types are SRAM, which uses flip-flops and is faster, and DRAM, which uses capacitors and must be refreshed. ROM is read-only and non-volatile, and its variants are PROM, which can be written once, EPROM, which is erased by ultraviolet light, and EEPROM, which is erased electrically. Cache memory sits between the CPU and main memory and is the fastest memory outside the registers. Secondary storage such as the hard disk, solid state drive, optical disc and flash drive is non-volatile and holds data permanently.

Units and types of computers

A bit is the smallest unit, a binary 0 or 1. Four bits make a nibble and eight bits make a byte, the unit that stores one character. Then 1024 bytes make a kilobyte, and the same multiple of 1024 gives the megabyte, gigabyte, terabyte, petabyte, exabyte, zettabyte and yottabyte in that order.

By working principle computers are analog, digital or hybrid; hybrid machines are common in hospitals, where an analog reading is converted to a digital value. By size and power they are microcomputers, minicomputers, mainframe computers and supercomputers. India entered supercomputing with PARAM 8000, built by C-DAC under Vijay Bhatkar in 1991.