class 9th Introduction of computer {computer notes} 2
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. The computer program for solving a specific problem is built right into the computer. Most analog computers are special purpose computers. These special purpose computers are widely used in industrial robotics.
Types of Computers
1. Analog Computers
Analog computers are used to process continuous data. Analog computers represent variables by physical quantities. Thus any computer which 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 cost more than 20 million rupees. In this computers 150 users are able to work on one C.P.U. The mainframes are able to process 1 to 8 bits at a time. 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 frm their desktop computers. A typical laptop computer has all the facilities available in microcomputer. The smallest laptops are called "PALMTOP".
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Generations of Computer
First Generation of Computer (1946-1959)
Main Features
Major Innovation - Vacuum Tubes
Main Memory - Punched Cards
Input Output Devices - Punched cards and papers
Languages - Low level machine language
Operating System - No operating system, human operators to set
switches
Size - Main frame for example ENIAC, EDVAC, UNIVAC
The duration lasted from 1946-1959 was based on vacuum tubes. These vacuum tubes were about the size of 100 watt light bulb and used as the internal computer component. However because thousands of such bulbs were used, the computers were very large and generate a large amount of heat, causing many problems in temperature regulation and climate control.
In this generation input and out put device (punched card) that was used fro data storing purpose were very slow. The computers were operating manually and the language used was a low level machine language (symbolic language) with binary code that required a high programming skill. ENIAC, EDVAC, UNIVAC and Mark-1 were some of the major inventions of this generation.
Advantages of First Generation
1. Vacuum tubes were used as electronic component.
2. Electronic digital computers were developed for the first time.
3. These computers were the fastest calculating devices of their time.
4. Computations were performed in millisecond.
Disadvantages of First Generation
1. Too large in size.
2. They were unreliable.
3. Induce a large amount of heat due to the vacuum tubes.
5. Not portable.
6. Limited commercial use.
Second Generation of Computers (1959-1964)
Main Features
Major Innovation - Transistors as main component.
Main Memory - RAM and ROM.
External Storage - Magnetic tapes and Magnetic Disk.
Input Output Devices - Magnetic tapes and Magnetic Disk.
Languages - Assembly language, some high level languages for Example BASIC, COBOL, FORTRAN.
Operating System - Human handles punched card.
Size - Main frame for example IBM-1401, NCR-300, IBM-600 etc.
The period of this generation is from 1959 to 1964. During this period transistor were used for internal logic circuits of computers. These computers could execute 200000 instructions per second. The input/output devices became much faster by the use of magnetic table. During this period the low level programing language were used however the high level programming languages such as FORTRAN and COBOL were also used. The problem of heat maintenance was solved and size of computer reduced, while speed and reliability were increased. Many companies manufactured second generation computers and many of those for business applications. The most popular second generation computer was IBM-1401, introduced in 1960, while the following computers were used by many business organizations. IBM-1400 series, IBM-1600 series, UNIVAC-III, NCR-300 etc.
Advantages of Second Generation
1. Smaller in size as compares to 1st generation.
2. Much more reliable.
3. Less heat generated.
4. Computation was performing in micro second.
5. Less hardware and maintenance problem.
6. Could be used for commercial use.
Disadvantages of Second Generation
1. Very costly for commercial use.
2. It still required frequent maintenance.
3. Frequent cooling also required.
Third Generation of Computers (1965-1970)
Main Features
Major Innovation - Integrated circuit (ICs) as basic electronic component.
Main Memory - PROM and DRAM.
External Storage - Improve disk (Floppy Disk)
Input and Output Devices - Keyboard for input, monitor for output.
Languages - More high level languages.
Operating System - Complete operating systems were introduced.
Size - Mini, for example: IBM SYSTEM / 360, ICH-360, HONEY WELL-316 etc.
In this generation the integrated circuits (IC) were used. Integrated circuits contain many electronic components on a single chip. The disk oriented systems wee made at the end of this generation. The size of computer became very small with better performance and reliability. High level programming languages were extensively used. In 1969 the first microprocessor chip INTEL 4004 was developed but it was used only in calculators. The faster input/output devices made possible multi-processing and multi programming. Where by a number of input terminals could be run virtually at the same time on a single centrally located computer. The famous computer were IBM-360, IBM-370, UNIVAC 9000 series etc.
Advantages of Third Generation
1. Smaller in size as compared to second generation.
2. More reliable.
3. Portable
4. Less electricity consumption.
5. Heat generation was rare.
6. General purpose computer.
Disadvantages of Third Generation
1. Air conditioning was required in many cases due to ICs.
2. Very advance technology was required to make the ICs.
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