Introduction To Computer

Computer 

A Computer is an automatic electronic, calculating device which can process a given input in a prescribed manner to produce a desired output, at a very high speed with remarkable accuracy. It can also perform all arithmetic and logical functions according to instructions given in a systematic order to solve specific problem and produce processed information.

Advantages of Computers

·        Speed

 Since Computer is an electronic machine and electrical pulses travel at the rate of passage of electric current. This speed enables the computer to perform millions of calculations per second.

·        Storage

 A computer has too much storage capacity. Once recorded, a piece of information can never be forgotten.

·        High Accuracy

 A computer can be considered as 100% accurate. Checking circuits are built directly into the computer, that computer errors thatundetected are extremely rare.

·        Versatility

 Computer can perform any task, provided it can be reduced to a series of logical steps.

· Decision Making Capability

 Computer can take simple decisions, such as less than, greater than or equal to. It also determines whether a statement is true or false.

Hardware

The physical components and other attached input and output devices of computers are called Hardware. All Hardware components may be connected mechanically, electrically or electronically with each other. Hardware includes input/output devices, CPU, backing storage devices and electronic circuit.

Software

Computer required a number of instructions to do tasks. The set of these instructions forms programs. Numbers of programs are combined for some purposes are called software. They are designed by manufactures and programmers.

Types of Software

1.     1.  System Software

2.     2. Application Software

Ages of Computer 

At the early age people used stones, sticks, symbols and finger tips to count, which were later replaced by numbers. The history of computing is divided into three ages during which man invented and improved different types of calculating machines. These ages are,

·        Dark age - 300 BC to 1890

·        Middle age - 1890 AD to 1944

·        Modern age - since 1944 AD

Dark Age (3000 BC to 1890 AD)

ABACUS

 About 3000 years BC, Chinese developed the first calculating machine named Abacus. Abacus consists of a rectangular wooden frame having rods which carry round beads. Counting is done by shifting the beads from one side to another.

OUGHTRED’S SLIDE RULES

 In 1632 AD William Oughtred, an English mathematician developed a slide rule. This device consists of two movable rules placed side by side on which number were marked.

PASCAL’S CALCULATOR 

 Blasé Pascal (1623-1662), a  French developed the first mechanical calculating machine in 1642. This machine consists of gears,wheels and dials. It was capable of adding and subtracting operations.

GOTTEFRIED WILHOLM LEIBNITZ

 In 1671, a German, Gottfried Von Leibnitz (1646-1716) improved Pascal’s calculator to make it capable of performing all maths operations.

Middle Age (1890 AD TO 1944 AD)

DOCTOR HERMAN HOLLERITH

 In 1880s Herman Hollerith an American developed a machine which used punch card system. The machine could sense and punch holes, recognize the number and make required calculations. This machine was first used in 1890s by American Census Bureau.

HOWARD AIKEN- MARK-1 COMPUTER 

 In 1937, Professor Howard Aiken build the first electro-mechanical computer Mark-1, by trying to combine Babbage’s theory and Hollerith’s punching technologies. He completed his project in 1944 with the help of IBM Engineers. Mark 1 could multiply two, twenty digit numbers in 5 seconds and made a lot of noise.

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ABC (ATANASOFF BERRY COMPUTER)

 ABC a special purpose computer was developed in 1938 by Dr. John Vincent Atanasoff and Clifford Berry at Iowa State College,USA.

Modern Ages (Since 1944 AD)

JOHN VON NEUMAN

 In 1945, Dr. John Von Neuman suggested the concept of Automatic Data Processing (ADP) according to the stored program and data.

FIRST ELECTRONIC COMPUTER

 Electronic Numerical Integrator And Calculator (ENIAC) was the first electronic computer made in 1946 by John Presper Eckert andJohn Williams Mauchly, at the University of Pennsylvania, USA. This was based on decimal number system and it has no memory. It could perform 5000 additions or 350 multiplications in one second. It contained 18000 vacuum tubes, 70,000 resistors, 10,000capacitors and 60,000 switches and occupied a two room car garage. It consumed 150 kW of power. It weighed 27 tons.

EDSAC (FIRST STORED PROGRAM COMPUTER)

 Electronic Delay Storage Automatic Computer (EDSAC) was first computer based on stored program concept. It was completed by Mourice Wilkes at Cambridge University in 1949.

EDVAC

 Electronic Discrete Variable Automatic Computer (EDVAC) was built by John Williams Mauchly, John Presper Eckert at MooreSchool, Pennsylvania in 1951.

UNIVAC (FIRST COMMERCIAL COMPUTER)

 Universal Automatic Computer (UNIVAC) was the first commercially used computer made by John Presper Eckert and JohnWilliams Mauchly in June 14, 1951.

Classification of Computers According to Purpose

1. General Purpose Computers

General purpose computers are designed to solve a large variety of problems. The different programs can be used to solve many problems. Most digital computers are general purpose computers and used in business and commercial data processing.

2. Special Purpose Computers

A computer designed for machine control or process control would be different than a general purpose computer. The special purpose computers are designed to solve specific problems. Most analog computers are special purpose computers. These special purpose computers are widely used in industrial robotics etc.

Types of Computers

1. Analog Computers

Analog computers are used to process continuous data. Analog computers represent variables by physical quantities. Thus these computers solve problem by translating physical conditions such as flow, temperature, pressure, angular position or voltage into related mechanical or electrical related circuits as an analog for the physical phenomenon being investigated in general it is a computer which uses an analog quantity and produces analog values as output. Thus an analog computer measures continuously. Analog computers are very much speedy. They produce their results very fast. But their results are approximately correct. All the analog computers are special purpose computers.

2. Digital Computers

Digital computer represents physical quantities with the help of digits or numbers. These numbers are used to perform Arithmetic calculations and also make logical decision to reach a conclusion, depending on, the data they receive from the user.

3.     Hybrid Computers

Various specifically designed computers are with both digital and analog characteristics combining the advantages of analog and digital computers when working as a system. Hybrid computers are being used extensively in process control system where it is necessary to have a close representation with the physical world. The hybrid system provides the good precision that can be attained with analog computers and the greater control that is possible with digital computers, plus the ability to accept the input data in either form.

Classification of Computers According to Size

1. Super Computers

Large scientific and research laboratories as well as the government organizations have extra ordinary demand for processing data which required tremendous processing speed, memory and other services which may not be provided with any other category to meet their needs. Therefore very large computers used are called Super Computers. These computers are extremely expensive and the speed is measured in billions of instructions per seconds.

2. Main Frame Computers

The most expensive, largest and the most quickest or speedy computer are called mainframe computers. These computers are used in large companies, factories, organizations etc. the mainframe computers are the most expensive computers They have several hundreds of megabytes of primary storage and operate at a speed measured in nano second.

3. Mini Computers

Mini computers are smaller than mainframes, both in size and other facilities such as speed, storage capacity and other services. They are versatile that they can be fitted where ever they are needed. Their speeds are rated between one and fifty million instructions per second (MIPS). They have primary storage in hundred to three hundred megabytes range with direct access storage device.

4.     Micro Computers

These are the smallest range of computers. They were introduced in the early 70’s having less storing space and processing speed. Micro computers of todays are equivalent to the mini computers of yesterday in terms of performing and processing. They are also called “computer of a chip” because its entire circuitry is contained in one tiny chip. The micro computers have a wide range of applications including uses as portable computer that can be plugged into any wall.

5. Laptop Computers

The smallest computer in size has been developed. This type of small computers look like an office brief case and called "LAPTOP" computer. The laptops are also termed as "PORTABLE COMPUTERS." Due to the small size and light weight, they become popular among the computer users. The businessmen found laptop very useful, during traveling and when they are far away from their desktop computers. A typical laptop computer has all the facilities available in microcomputer.