Computer is a machine which accepts the data or information in raw formats (digital format) process this data according to the given order of instructions and produces the desired output. Computer is composed of four main components those are Memory, ALU (Arithmetic and logic unit), Control unit, input and output devices (Peripheral devices). These components are interconnected to each other with Busses (group of wires).
Memory is a collection of registers which are used to store the processed data. Reading and writing data in Memory takes very less time as compared to Main memory. In order to increase computer speed, data which is needed most frequently is stored in this memory. There are two types of memory. First is Random-Access Memory (RAM) second is Read Only Memory (ROM). RAM can be modified but ROM is permanent i.e. anything written in RAM can be changed whereas nothing can be written or added or deleted in ROM. ROM is pre loaded with data at the time of manufacturing. Initial start-up instructions of computer are stored in ROM.
RAM is volatile (contents gets erased when power is turned off) whereas ROM is non volatile.
ALU (Arithmetic and Logic Unit): ALU is used to carry out the Arithmetic and logical operations on the data.
Arithmetical operations such as addition, subtraction, Multiplication, division, trigonometry functions (sine, cosine, tangent) and square roots are performed by ALU on integers and floating point (real numbers are depicted as floating point) within no time. Logical operations such as AND, OR, XOR and NOT can also be performed easily.
The Control unit is the brain of CPU. It controls the working of the other devices. When the program is given as the input through input device the control unit read it and decodes the program and based on instructions either sends sequence of signals to the other devices stores the resultant data into memory. There are different types of control units,one is the hardwired control unit the other one is known as microprogrammed control unit. Hardwired control units are made of digital circuits; once the hardwired control unit is constructed it cannot be modified whereas microprogrammed control unit can be modified according to the instructions in microprograms.
Memory, ALU, Control Unit together constitutes CPU (Central Processing Unit).
Peripheral Devices (Input and output devices): Input and Output devices are required for establishing communication between the computer and user. Input devices as the name indicates are required to provide information to the computer and output devices are used to display information to user. Keyboard , Mouse , Microphone, Joysticks ,scanners digital cameras ,Barcode Readers, Webcam ,Laser rangefinder are known as input devices ; Monitor (Display), Printer and Speakers are known as output devices.
ENIAC (Electronic Numerical Integrator And Calculator) was the first digital computer which was invented at the University of Pennsylvania by J. Presper Eckert and John Mauchly. It was a really huge machine made of 18000 vacuum tubes, weighing almost 50 tons and occupied area of 1,800 square feet. Whirlwind machine was the first digital computer with magnetic core RAM and Real-time graphics introduces by MIT. Electronic Delay Storage Automatic Calculator (EDSAC) was the first stored program electronic computer and first computer that supports graphical computer game. It was invented in England at University of Cambridge.Kenback-1 was the first personal computer introduced in 1971. In Kenback-1 sequence of switches were used for inputting data and output was display by turning on or off the sequence of lights. Osborne I was the first compact computer made by Adam Osborne in 1981 which had 5 inch display CRT, two floppy drives with memory of 64 KB and a modem. Today’s computers are much faster and more capable than early computer machine with very less occupied space. Now a day’s computers (P Cs) are as small as plam tops, some of them can be easily be fitted in mobiles too. Embedding computers are seen in every device ranging from toys to washing machines and from defence purposes like aircrafts to industrial purpose like robotic manufacturing machines.