dear learners in this unit we will introduce you to computer and its users capabilities and limitations of computers classification of computers types of computers history and evolution of computers basic operations of computers and organization of computers when you have completed this unit you must be able to explain what is a computer basic units of computer and their purpose how computers work features of computers uses of computers types of computers generations of computers applications of computers and basic computer operations now we will discuss some characteristics of computers some features of computers are high speed reliability accuracy large memory logical decision making versatility automation and diligence first feature of computer is its speed the speed of personal computer is measured in terms of megahertz that is millions of clock cycles generated by microprocessor clock and one second most modern micro computers are rated from 300 megahertz to gigahertz a typical 800 megahertz computer takes a very small fraction of a second to complete one cycle normally several clock cycles are required to fetch a single instruction from memory decoded and executed the speed of workstations mainframes and high-speed personal computers is measured in terms of millions of instructions per second these computers operate in the range of 20 to 1,000 MIPS typically a hundred MIT's computer can execute 100 million instructions per second the speed of supercomputer is measured in terms of floating-point operations per second floating-point numbers include very small or very large numbers supercomputers operate at a speed of 500 gigaflops to 3 teraflops a gigaflop is 1 billion flops and a tariff now we will discuss some characteristics of computers some features of computers are high speed reliability accuracy large memory logical decision making versatility automation and diligence first feature of computer is its speed the speed of personal computer is measured in terms of megahertz that is millions of clock cycles generated by microprocessor clock in one second most modern micro computers are rated from 300 megahertz to gigahertz a typical 800 megahertz computer takes a very small fraction of a second to complete one cycle normally several clock cycles are required to fetch a single instruction from memory decoded and executed the speed of workstations mainframes and high speed personal computers is measured in terms of millions of instructions per second these computers operate in the range of 20 to 1,000 MIPS typically a hundred MIT's computer can execute 100 million instructions per second the speed of supercomputer is measured in terms of floating-point operations per second floating-point numbers include very small or very large numbers supercomputers operate at a speed of 500 gigaflops to 3 teraflops a gigaflop is 1 billion flops and a teraflop is equal to 1 trillion flops second and the most important feature of computer is reliability and accuracy the results of computers are highly reliable and precise Computers maintain accuracy within a millisecond microsecond nanosecond picosecond or any level of required precision these are also accurate up to many decimal places than mathematical calculations high accuracy and reliability is because a computer works on electrical pulses that rarely fail to convey correct information the reliability of computers is maintained especially in repetitive tasks further the error checking systems are built in the computer to reduce the chance of errors organizations provide backup computers that automatically take over in case the main computer fails recovery systems are implemented to further strengthen the reliability of data dear learners another feature of computer is its large memory computer memory is used to store data and information temporarily or permanently temporary memory is normally referred to as random access memory this is used to temporarily store programs that are currently executing on your system the contents of RAM are erased when the bar is off normally the size of temporary memory is measured in terms of kilobytes and megabytes most modern computers and special graphics computers have large memories in multiples of gigabytes permanent memory is used to permanently store large repositories of data user programs applications like MS Office and operating systems like ms windows or unix an example of permanent storage is hard disk the programs stored on permanent memory are available when you switch on the computer large amount of data can be stored on permanent storage devices computer memories have another advanced feature to dynamically access any data irrespective of its storage location apart from computations a computer has the ability to take decisions the computer has special circuits to perform logical operations logical operations include comparisons such as a number is equal to greater than or less than another number depending upon the results of logical operations a computer can take appropriate actions computer is also capable of comparing text images and even audio the decision-making capabilities of computer has led to the invention of artificial intelligent machines computer is a versatile machine it is capable of solving a variety of problems the use of personal computers have considerably grown in the fields of communications multimedia scientific research designing engineering education and entertainment another remarkable feature of computers is its ability to perform operations automatically when the computer is switched on it automatically executes instructions to check all peripheral devices loads the operating system and provides interface to the user without human interaction computer is a diligent machine it never feels tiredness you can complete different jobs or a single task repeatedly without losing position some computer systems are rarely down in several years these can process data continuously and accurately dear learners although computers are widely used due to their versatility but computers have certain limitations some limitations of computers are lack of intelligence need of proper environment for smooth operation and need of special language the first limitation of computer is its lack of intelligence although a computer can perform logical operations at a very fast speed but it is unable to think like a human presently computers cannot tell the fragrance of a flower or have no aesthetic sense computers need proper environment for smooth operations these can only operate dust-free environment under certain temperature conditions computers can only understand binary codes that is zeros ones and their combinations these codes are not commonly used by humans special software interpreters and compilers are used to convert natural languages to computer understandable codes despite these limitations the popularity and applications of computers are considerably growing dear learners the quest for a mechanical servant that could free people from tedious aspects of thinking is centuries-old it started with the introduction of abacus some 5000 years ago abacus is considered the original manual counting device it is still used in education to demonstrate the principles of arithmetic this device contains beads on rods calculations are made by positioning the beads upward or downward dear learners now we will discuss the contributions of scientists professionals and students who contributed to bring to us this marvel of the modern age in 1642 French mathematician and philosopher Blaise Pascal invented Pascaline it used wheels like telephone dials numbers were arranged on these dials wheels were evolved to make calculations in eighteen hundred and one French Weaver named Joseph Marie jacquard created jacquard loom punched cards were used to direct the movement of needles thread and fabric to create different patterns in a fabric on hand known as jacquard weaves efforts were made by different scientists across the world and in 1842 Charles Babbage introduced Difference Engine and then an analytical engine it was a general-purpose computer that could add subtract divide and multiply an automatic sequence it's average speed was 60 additions per second the idea of Babbage was further refined and improved by Lady ADA Augusta Lovelace she proposed that punched cards could be used to instruct Babbage's engine to perform repetitive tasks children of valuable contributions she is considered as a first programmer during 1890 dr. Herman Hollerith developed the first electromechanical punch card tabulating machine hand punch was used to enter data into cards a soldier box was used to read and search these cards the output was summarized on tabulating dials Hollerith and handsome income by losing his machinery to the governments of the USA Canada Austria and others his invention led to the concept of modern data processing Hollerith is also the founder of tabulating machine company that later on became IBM dear learners sophisticated punch cloud devices were introduced from 1920 to 1950 the electromechanical accounting machine family included Cod punch verifier reproducer summary punch interpreter sorter collateral and accounting machines these machines were very large heavy unrequired physical labor operate the first modern digital computer Atanasoff baby computer was built in Iowa State University campus between 1939 and 1942 the development team was led by John Atanasoff professor of physics and mathematics and a graduate student Clifford berry this machine included many features like binary arithmetic parallel processing storage and computer functions it weighed about 750 pounds and could store about 3,000 bits of data in the early 40s the first electromechanical computer mark 1 was developed by Harvard University professor Howard I can dear learners sophisticated punch cloud devices were introduced from 1920 to 1950 the enriching mechanical accounting machine family included Cod punch verifier reproducer some early punch interpreter sorter collateral and accounting machines these machines were very large heavy unrequired physical labour to operate the first modern digital computer Atanasoff belly computer was built in Iowa State University campus between 1939 and 1942 the development team was led by John Atanasoff professor of physics and mathematics and a graduate student Clifford berry this machine included many features like binary arithmetic parallel processing storage and computer functions it weighed about 750 pounds and could store about 3,000 bits of data in the early 40s the first electromechanical computer mark 1 was developed by Harvard University professor Howard I can IBM sponsored the development of this huge machine in 1946 first a large scale digital computer the electronic numerical integrator and computer was developed this was developed by John Mauchly and John presper eckert an engineer at MU School of Electrical Engineering in the University of Pennsylvania ENIAC was used to prepare firing and bombing tables for the US Army and Navy it was also used in secret research that was aimed at building powerful and destructive bombs in LAC consisted of 30 separate units power supply and air cooling system it weighed 30 tons used 19,000 vacuum tubes 1500 relays and hundreds of thousands of resistors capacitors and inductors it required a large amount of electricity it could perform 5,000 additions per minute and hundreds of multiplications per minute another important digital computer in history was Colossus one it was built at a secret government research establishment in England under the direction of professor max Newman it was designed to break German Enigma codes during World War two it could scan and analyze 5000 characters per second Colossus became operational in December 1943 and proved to be one of the most important technological aids to victory in World War two in 1949 exact was introduced this was capable of storing computer program in 1950 ed WAC was developed it could store you upper concede the idea of COBOL programming language it was a general-purpose English like programming language that is still used by many organizations dr. grace developed a compiler that translated programs written in Cobo to run on a variety of computers she is also the pioneer to find first real bug in a computer programmers debug software's to find out errors or bugs in their programs second-generation computers were introduced during 1959 things were built by using transistors instead of vacuum tubes these computers were more powerful reliable less expensive and smaller in size than their predecessors until early 60s large companies were producing mainframe computers in 1963 dec introduced pdp-8 it was a transistor based mini computer the demand for small computers tremendously increased for business and scientific applications and by 1970 a number of firms were manufacturing computers dear learners technology was rapidly changing and third generation computers were introduced during 1964 these computers used large scale integrated circuits IBM developed system/360 with the idea of upward compatibility that allowed companies to upgrade their computer systems without converting their data besides developments in hardware technology scientists were busy in developing the techniques to interact with the computer to perform a variety of tasks in 1960 dr. Thomas Kurtz and dr. Johann Kamini started developing a programming language and introduced basic programming language in 1964 it became a popular programming language for business and scientific applications basic was supported on many types of computers during 1971 fourth generation computers were introduced with the introduction of integrated circuit this was significant innovation in the history of computing during early 70s Bill Gates and Paul Allen were busy in developing games for personal computers and introduced a basic programming language they affirmed today's most influential software from Microsoft Corporation it revolutionized the idea of personal computing with the introduction of Microsoft disk operating system dear learners personal computers were not available Apple - personal computer was introduced in 1975 this was a prominent venture by Stephen Jobs and Steve Wozniak in 1981 IBM introduced IBM personal computer and many personal computers were sold by the end of 1982 at that time many other companies started manufacturing of IBM pc compatibles the use of personal computers had considerably increased in business there was a tremendous need for business software Mitchell Kapoor established Lotus development company Lotus corporation introduced electronic spreadsheet application that boosted the sales of IBM PC and Lotus 1-2-3 dear learners the credit for today's easy-to-use point-and-click graphical user interface goes to Apple Computer gu I changed the human-computer interaction from text-based exchange mode to friendly wimp interface during the last two decades UNIX microsoft windows sun solaris apple macintosh and many other graphical user interface operating systems were introduced dear learners during the last few years there has been a tremendous advancement in microprocessor technology and now personal computers operate at speeds up to 2 gigahertz there has been a considerable advancement in computer peripheral devices most powerful supercomputers mainframes and minutes passed on risk and sisk computing technologies are available at speeds beyond imagination dear learners by the time you finish this course you may visualize drastic changes in computing technology around you