Introduction of computer system

Computer is derived from the latin word “Computare” which means ‘calculate’

Full form: Common Operated Machine Particularly Used for Technical Education and Research

Computer can be defined as an electronic digital and automatic machine which takes input from the user, processes it, stores it if necessary and gives output in desired form.a

Computer consists of main processing unit called Central Processing unit (CPU), input devices, output devices, main memory and auxiliary storage.

Architecture of Computer System

Input device

An input device is a hardware or peripheral device used to send data to a computer. An input device allows users to communicate and feed instructions and data to computers for processing, display, storage and/or transmission. Input devices includes mouse, keyboard, joystick etc.

Output devices

An output device is any device used to send data from a computer to another device or user. Most computer data output that is meant for humans is in the form of audio or video. Thus, most output devices used by humans are in these categories. Examples include monitors, projectors, speakers, headphones and printers. 

Storage devices

A storage device is any computing hardware that is used for storing, porting and extracting data files and objects. It can hold and store information both temporarily and permanently, and can be internal or external to a computer, server or any similar computing device. There are two different types of storage devices:

• Primary storage devices

Generally smaller in size, these are designed to hold data temporarily and are internal to the computer. They have the fastest data access speed, and include RAM and cache memory.

• Secondary storage devices

These usually have large storage capacity, and they store data permanently. They can be either internal or external to the computer, and they include the hard disk, optical disk drive and USB storage device.

Processor (CPU)

A processor is the logic circuitry that responds to and processes the basic instructions that drive a computer. The four primary functions of a processor are fetch, decode, execute and writeback.

Features of computer

Speed

In 1968, integrated Circuit was developed which contains no. of electronic components such as transistors and diodes which increased the speed of calculation.

Word length

In computer, word refers to the no. of bits that a processor can process as a single unit. Processors can have 8, 16, 32 or 64 bit word length.

Accuracy and reliability

Computer can do a lot of work without any mistakes and tiredness.

vast storage capacity

Computer can store and retrieve massive amounts of data. Computer Storages can be divided into primary storage and secondary storage.

Automatic

Computer is an automatic machine.

Diligent

The ability of a computer to perform a work repeatedly again and again without getting tired and bored is called diligence.

Versatile

a computer can perform more than one work having different characteristics.

Electronic

Computers can’t work without electricity. It is composed of electronic components such as transistor, diode, register etc.

No IQ

Computer does not work without instruction.

NO Feelings

Computer does not have emotions, knowledge, experience, feeling.

History of computer

The computer was born not for entertainment or email but out of a need to solve a serious number-crunching crisis. One of the earliest machines designed to assist people in calculations was the abacus which is still being used some 5000 years after its invention.

In 1642 Blaise Pascal (a famous French mathematician) invented an adding machine based on mechanical gears in which numbers were represented by the cogs on the wheels.

Englishman, Charles Babbage, invented in the 1830's a "Difference Engine" made out of brass and pewter rods and gears, and also designed a further device which he called an "Analytical Engine". His design contained the five key characteristics of modern computers:

1. An input device

2. Storage for numbers waiting to be processed

3. A processor or number calculator

4. A unit to control the task and the sequence of its calculations

5. An output device

There are five generations of computer

First Generation Computer (1945-1954)

1. Based on vacuum tubes.

2. Bigger in size

3. Consists of thousands of vacuum tubes for building cpu.

4. Overheating problem

5. Processing speed was very slow

6. Due to high cost, not used for commercials use

Examples: Mark I, UNIVAC, EDSAC, EDVAC, ENIAC etc.

Second Generation Computer (1955-1964)

1. Used transistors instead of vacuum tubes.

2. Smaller in size due to use of transistors.

3. Magnetic core memory was used as secondary memory.

4. Cheaper than first generation computers.

5. Manufactured for commercial purpose also.

Examples:  IBM 1401, ICL 2950/10.

Third Generation Computer (1965-1979)

1. Large no.  Of transistors could be fabricated in a silicon chip called as integrated circuit (ic).

2. Size reduced so that computers became portable.

3. Operating speed was in few megahertz (around 12mhz).

4. Semiconductor memory was used as primary storage.

5. High level language like c was used.

6. Multiprocessing operating system like Unix, Multics were introduced.

7. Keyboard and video display were introduced as input and output respectively.

Examples:  IBM 360, PDP-8, PDP-11, STAR etc.

Fourth Generation Computer(1980-Present)

1. Computers became portable.

2. Microprocessor was introduced.

3. Processing speed is very high, measured in gigahertz.

4. GUI operating system such as MS-windows, mac OS are used

5. Ai such as voice recognition, character recognition, robotics etc are used.

6. Multimedia, networking, distributed computing are introduced.

Examples: Pentium PC, Core2Duo PC, Core i7 Pc, Apple/Macintosh etc.

Fifth Generation Computer (present and onwards)

The ministry of International Trade and Industry of Japan initiated FGCS (fifth generation computer system) project in 1982.

1. will have IQ and logical power, decision making capability, expert system similar to human being.

2. will use parallel processing so that heavy processing will be possible.

3. Bio chips made up of protein fiber Gallium Arsenide(GaAs) will be used as memory devices.

4. Natural languages such as English, German, French and Sanskrit etc will be used as programming language.

Types of computer

A. Analog computer

An analog computer a computing system which represents numerical data using analog physical variables (speed, length, voltage, current, pressure.

Types of analog computer:

Mechanical

Pneumatic

Hydraulic

Electromechanical Electronic

The representation of mechanical analog computers is, for example, the number of turns of the gears of the mechanism. In the electric ones, differences in voltage are used.

They can perform operations such as addition, subtraction, multiplication, division, differentiation, integration and inversion. When working, analog computers simulate the process of computation, and the characteristics representing digital data are constantly changing with time.

B. Digital computer

An electronic computer in which the input is discrete rather than continuous, consisting of combinations of numbers, letters, and other characters written in an appropriate programming language and represented internally in binary notation.

Those computers work on a digital signal. These signals are used to represent data as a sequence of discrete values; at any given time, it can only take on one of a finite number of values.

Digital computers use the binary number system, which has two digits i.e., 0 and 1. A binary digit is called a bit. Here the information is represented in the groups of bits.

Difference between Analog and Digital Computer

Classification of digital computer on the basis of size, cost, power

Super computer

Supercomputers are one of the fastest computers currently available. Supercomputers are very expensive and are employed for specialized applications that require immense amount of mathematical calculations (number crunching).

For example, weather forecasting, scientific simulations, (animated) graphics, fluid dynamic calculations, nuclear energy research, electronic design, and analysis of geological data (e.g. in petrochemical prospecting).

Mainframe computer

Mainframe is very large in size and is an expensive computer capable of supporting hundreds or even thousands of users simultaneously. Mainframe executes many programs concurrently and supports many simultaneous executions of programs.

Minicomputer

It is a midsize multi-processing system capable of supporting up to 250 users simultaneously.  In the past decade, the distinction between large minicomputers and small mainframes has blurred, however, as has the distinction between small minicomputers and workstations. But in general, a minicomputer is a multiprocessing system capable of supporting from up to 200 users simultaneously.

Microcomputer
A microcomputer is a computer with a central processing unit (CPU) as a microprocessor. Designed for individual use, a microcomputer is smaller than a mainframe or a minicomputer.

The term microcomputer is not as commonly used as it was during the 1970s-1980s. We now refer to microcomputers as, simply, computers, or personal computers (PC).

Classification of micro computer

Workstations

Also known as desktop machines, workstations are mostly used for intensive graphical applications. Compared with personal computers, they have more processor speed. They use sophisticated display screens that feature high-resolution color graphics.

Personal Computers

Also called PCs or home computers, the personal computers are very popular computer systems. They are more affordable and easier to use than workstations. They are self-sufficient computers intended for one user. Most often used for database applications and word processing.

Laptop Computer

Laptop Computer or notebook computers are portable computers that are mainly carried in a briefcase.  They are wonderfully functional and portable, and popular with travelers who require a computer every place they visit.

Mini PC

Mini PCs are tiny computers that can fit in the palm of your hand. An example of Mini PC is pen-based computers that use a pen-like stylus. Special hardware design techniques make them smaller, portable and light weight computers.

C. Hybrid computer

A hybrid computer is a type of computer that offers the functionalities of both a digital and an analog computer. It is designed to include a working analog unit that is powerful for calculations, yet has a readily available digital memory. In large industries and businesses, a hybrid computer can be used to incorporate logical operations as well as provide efficient processing of differential equations.

Hybrid computers are well known for their ability to blend analog and digital features of computers. Advantages include the availability of both analog and digital computations within a single unit and an efficient processing speed. A hybrid computer is individually designed and integrated, taking into consideration the field of its application and processing requirements. A hybrid computer is constructed in such a way that its components make the device fast and accurate.

Examples:  Gas Pump Station (where measurement of gas by analog system, and displaying such calculation by digital system (computer).