COMPUTER SCIENCE

1. COMPUTER SCIENCE 1.0 Introduction to Computers

2. 1.1 INTRODUCTION • In the beginning of civilization, people used fingers and pebbles for computing purposes. With the growth of civilization, the computing needs also grew. • The need for a mechanism to perform lengthy calculations led to the invention of the first calculator and then the computers. • In simple words, a computer is an electronic device that performs mathematical and non-mathematical operations with the help of instructions to process the data to achieve desired results.

3. 1.2 CHARACTERISTICS OF COMPUTERS • Characteristics which make computers an essential part of every emerging technology and such a desirable tool in human development. • Speed: The computers process data at an extremely fast rate. • Accuracy: Besides being efficient, the computers are also very accurate. • Reliability: Computers have built-in diagnostic capabilities which help in continuous monitoring of the system. • Storage Capability: Computers can store large amounts of data and it can recall the required information almost instantaneously.

4. 1.2 CHARACTERISTICS OF COMPUTERS • Characteristics continued … • Versatility:Computers can perform multiple tasks simultaneously with equal ease—at one moment it can be used to prepare a letter, at the other moment it can be used to play music and in between one can print a document as well(by changing the sequence of instructions). • Diligence: Computer, being a machine, does not suffer from the human traits of tiredness and lack of concentration. • Resource Sharing: A computer used to be an isolated machine, but today's computers have the capability to connect with each other. Apart from device sharing (printers), data and information can also be shared among groups of computers, thus creating a large information and knowledge base.

5. 1.2 LIMITATIONS OF COMPUTERS • As a machine, it can perform only what it is programmed to do; nothing more and nothing less. It needs well-defined instructions to perform any operation. • Although processing has become less tedious with the development of computers, it is still time-consuming and an expensive job. • Computer parts require regular checking and maintenance to give correct results. • Computers need to be installed in a dust-free place, and some parts of the computers get heated up due to heavy processing.

6. 1.3 EVOLUTION OF COMPUTERS • Introduction • In ancient times, people used fingers to perform the calculations such as addition and subtraction. Soon, mankind realized that it would be easier to do calculations with pebbles as compared to fingers. • Consequently, pebbles were used to represent numbers, which led to the development of sand tables. • They are known to be the earliest device for computation.

7. 1.3 EVOLUTION OF COMPUTERS • Sand Tables • A sand table consists of three grooves in the sand with a maximum of 10 pebbles in each groove. To increase the count by one, a pebble has to be added in the right-hand groove. • When 10 pebbles were collected in the right groove, they were removed and one pebble was added to the adjacent left groove.

8. 1.3 EVOLUTION OF COMPUTERS • Abacus • Abacus emerged around 5000 years ago in Asia Minor and it is still in use in some parts of the world. • An abacus consists of sliding beads arranged on a rack, which has two parts: upper and lower.

9. 1.3 EVOLUTION OF COMPUTERS • Napier Bones • In 1614, John Napier, a Scottish mathematician, made a more sophisticated computing machine called the Napier bones (made of the strips of ivory bones). • This was a small instrument made of 10 rods on which the multiplication table was engraved. • This device enabled multiplication in a fast manner.

10. 1.3 EVOLUTION OF COMPUTERS • Slide Rule • The invention of logarithms influenced the development of another famous invention known as slide rule (in 1620 AD). • It was based on the principle that actual distances from the starting point of the rule is directly proportional to the logarithm of the numbers printed on the rule.

11. 1.3 EVOLUTION OF COMPUTERS • Pascaline • In 1642 AD, Blaise Pascal, a French mathematician, scientist and philosopher, invented the first functional automatic calculator. • It had a complex arrangement of wheels, gears and windows for displaying numbers.

12. 1.3 EVOLUTION OF COMPUTERS • Stepped Reckoner • In 1694, Gottfried Wilhem von Leibniz, a German mathematician, extended the Pascal's design to perform multiplication and division and to find square root. • It was the first mass-produced calculating device, which was designed to perform multiplication by repeated additions.

13. 1.3 EVOLUTION OF COMPUTERS • Punch Card System • In 1801, Joseph Marie Jacquard, a French textile weaver, invented a power loom with an automatic card reader. • This power loom used a series of cards with holes punched at different positions. To automate the weaving process, these cards were placed between the needles and the thread, thereby creating different patterns. • This idea of using punched cards to communicate with machines was an important step in the development of computers.

14. 1.3 EVOLUTION OF COMPUTERS • Punch Card System • The presence or absence of a hole in a punched card represented the two digits of the binary system, which is the base for all modern digital computers.

15. 1.3 EVOLUTION OF COMPUTERS • Difference Engine • In 1822, Charles Babbage, a professor of mathematics, devised a calculating machine known as difference engine, which could be used to mechanically generate mathematical tables. The difference engine can be viewed as a huge complex abacus. • Babbage never made a fully functional difference engine and in 1833, he quit working on this machine to concentrate on the analytical engine.

16. 1.3 EVOLUTION OF COMPUTERS • Analytical Engine • Analytical engine is considered to be the first general-purpose programmable com • Babbage's innovation in the design of the analytical engine made it possible to test the sign of a computed number and take one course of action if the sign was positive and another if the sign was negative. • Babbage also designed this device to advance or reverse the flow of punched cards to permit branching to any desired instruction within a program.

17. 1.3 EVOLUTION OF COMPUTERS • Lady Ada Lovelace • Lady Ada Lovelace, a fellow mathematician, helped Babbage in the development of the analytical engine. • She not only helped him with financial aid, but also wrote articles and programs for the proposed machine. • Due to her contributions, she is known as the 'first programmer'.

18. 1.3 EVOLUTION OF COMPUTERS • Hollerith's Tabulator • Herman Hollerith invented the punched-card tabulating machine to process the data collected in the United States' census. • In 1896, Hollerith founded the Tabulating Machine Company, which was later named as IBM (International Business Machines).

19. 1.3 EVOLUTION OF COMPUTERS • Other Developments • In 1904, Sir John Ambrose Fleming worked to develop the first thermionic valve, which is also known as vacuum tube. Fleming named the device 'a valve' because it allowed electrical currents to pass only in one direction. Since this is a two-element vacuum tube, it was also called as diode. These diodes were the cornerstone of the first-generation computers. • In 1906, Lee de Forest, an American inventor, introduced a third electrode into the diode. The resulting triode could be used both as an amplifier and a switch and its ability to act as a switch created a tremendous impact on digital computing.

20. 1.3 EVOLUTION OF COMPUTERS • Other Developments • In 1931, Vannevar Bush, an American electrical engineer, built the differential analyser to solve differential equations. • In 1938, Claude Shannon, a student at MIT, recognized the connection between electronic circuits and Boolean algebra. He transferred the two logic states to electronic circuits by assigning different voltage levels to each state. • Shannon also provided electronics engineers with the mathematical tool they needed to design digital electronic circuits. These techniques remain the cornerstone of digital electronic design to this day.

21. 1.3 EVOLUTION OF COMPUTERS • Some Early Computers • MARK-I Computer • From the year 1937 to 1944, Howard Aiken, an American mathematician, under the sponsorship of IBM, developed MARK-I. It was essentially a serial collection of electromechanical calculators and had many similarities to Babbage's analytical machine. • MARK-I was capable of performing addition, subtraction, division, multiplication and table reference. • However, it was extremely slow, noisy and bulky (approximately 50 ft long, 8 ft high and weighed 5 tons).

22. 1.3 EVOLUTION OF COMPUTERS • Some Early Computers • ABC Computer • In 1939, John Vincent Atansoft and Clifford Berry formulated the idea of using the binary number system to simplify the construction of an electronic calculator. At the end of 1939, they built the first electronic computer named as ABC (Atansoft Berry Computer). • It is considered the first computing machine, which introduced the idea of binary arithmetic, regenerative memory and logic circuits. • This computer used electronic vacuum tubes and the circuitry was based on George Boole's Boolean algebra.

23. 1.3 EVOLUTION OF COMPUTERS • Some Early Computers • Colossus • In 1944, Alan Mathison, a British mathematician, along with some colleagues, created a computer called the colossus, which comprised 1800 vacuum tubes. • It was one of the world's earliest working programmable electronic digital computers. Colossus was a special-purpose machine that suited a narrow range of tasks. • Although colossus was built as a special-purpose computer, it proved flexible enough to be programmed to execute a variety of routines.

24. 1.3 EVOLUTION OF COMPUTERS • Some Early Computers • ENIAC • In 1946, John Eckert and John Mauchly of the Moore School of Engineering at the University of Pennsylvania developed Electronic Numerical Integrator and Calculator (ENIAC). • It embodied almost all the components and concepts of today's high-speed, electronic digital computers. • ENIAC consisted of 18,000 vacuum tubes and weighed nearly 30 tons. • It could compute at a speed 1000 times that of Mark-I, but had a limited amount of space to store and manipulate information.

25. 1.3 EVOLUTION OF COMPUTERS • Some Early Computers • EDVAC • In 1949, John Eckert and John Mauchly also proposed the development of Electronic Discrete Variable Automatic Computer (EDVAC). • The EDVAC was the first electronic computer to use the stored program concept introduced by John Von Neumann. It also had the capability of conditional transfer of control, that is, the computer could stop any time and then resumed again. • EDVAC contained approximately 4000 vacuum tubes and 10,000 crystal diodes.

26. 1.3 EVOLUTION OF COMPUTERS • Some Early Computers • EDSAC • The Electronic Delay Storage Automatic Calculator (EDSAC) was also based on John Von Neumann's stored program concept. • EDSAC had 3000 vacuum valves arranged on 12 racks and used tubes filled with mercury for memory. • It could carry out only 650 instructions per second. A program was fed into the machine through a sequence of holes punched into a paper tape. • The machine occupied a room, which measured 5 meters by 4 meters.

27. 1.3 EVOLUTION OF COMPUTERS • Some Early Computers • UNIVAC • The Universal Automatic Computer (UNIVAC) was the first commercially available electronic computer. • It was also the first general-purpose computer, which was designed to handle both numeric and textual information. • It was manufactured by the Eckert-Mauchly Corporation in 1951 and its implementation marked the real beginning of the computer era. • Magnetic tapes were used as input and output media at a speed of around 13,000 characters/s. • The machine was 25 by 50 ft in length, contained 5600 tubes, 18,000 crystal diodes and 300 relays.

28. 1.4 GENERATIONS OF COMPUTERS • In computer terminology, the word 'generation' is described as a stage of technological development or innovation that fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper, more powerful, more efficient and reliable devices. • According to the type of 'processor' installed in a machine, there are five generations of computers.

29. 1.4 GENERATIONS OF COMPUTERS • First Generation (1940–56)—Vacuum Tubes • First-generation computers were vacuum tubes/thermionic valves-based machines using vacuum tubes for circuitry and magnetic drums for memory. • A magnetic drum is a metal cylinder coated with magnetic iron oxide material on which data and programs can be stored. • The input was based on punched cards and paper tape and the output was in the form of printouts.

30. 1.4 GENERATIONS OF COMPUTERS • First Generation (1940–56)—Vacuum Tubes • First-generation computers relied on binary-coded language, which is also known as the machine language (i.e. language of 0s and 1s), to perform operations and were able to solve only one problem at a time. • Each machine was fed with different binary codes and hence was difficult to program. This resulted in lack of versatility and speed. In addition, to run on different types of computers, instructions must be rewritten and recompiled. • Examples: ENIAC, EDVAC and UNIVAC.

31. 1.4 GENERATIONS OF COMPUTERS • Second Generation (1956–63)—Transistors • Second-generation computers used transistors instead of vacuum tubes, which were superior to vacuum tubes. A transistor is made up of semiconductor material. • It usually had three leads and performed electrical functions such as voltage, current or power amplification with low power requirements. • Since transistor is a small device, the physical size of the computer was greatly reduced. Computers became smaller, faster, cheaper, energy-efficient and more reliable than their predecessors.

32. 1.4 GENERATIONS OF COMPUTERS • Second Generation (1956–63)—Transistors • One of the major developments of this generation includes the progress of machine language to assembly language. Assembly language used mnemonics (abbreviations) for instructions rather than numbers; for example, ADD for addition and MULT for multiplication. • As a result, programming became less cumbersome. Early high-level programming languages such as COBOL and FORTRAN also came into existence during this period. • Examples: PDP-8, IBM 1401 and IBM 7090.

33. 1.4 GENERATIONS OF COMPUTERS • Third Generation (1964–Early 1970s)—Integrated Circuits • The development of the integrated circuit was the trait of the third-generation computers. An integrated circuit, also called IC, consisted of a single chip (usually silicon) with many components such as transistors and resistors fabricated on it. • Integrated circuits replaced several individually wired transistors. This development made computers smaller in size, reliable and efficient.

34. 1.4 GENERATIONS OF COMPUTERS • Third Generation (1964–Early 1970s)—Integrated Circuits • Instead of punched cards and printouts, users interacted with third-generation computers through keyboards and monitors and interfaced with an operating system. • This allowed the device to run many different applications at one time with a central program that monitored the memory. • For the first time, computers became accessible to majority of common people because they were smaller and cheaper than their predecessors. • Examples: NCR 395 and B6500.

35. 1.4 GENERATIONS OF COMPUTERS • Fourth Generation (Early 1970s–Till Date)—Microprocessors • Fourth generation is an extension of third-generation technology. • Although, the technology of this generation is still based on the integrated circuit, these have been made readily available because of the development of the microprocessor (circuits containing millions of transistors).

36. 1.4 GENERATIONS OF COMPUTERS • Fourth Generation (Early 1970s–Till Date)—Microprocessors • Fourth-generation computers led to an era of large-scale integration (LSI) and very-large-scale integration (VLSI) technology. • LSI technology allowed thousands of transistors to be constructed on one small slice of silicon material, whereas VLSI squeezed hundreds of thousands of components on to a single chip. • Ultra-large-scale integration (ULSI) increased that number to millions. This way the computers became smaller and cheaper than ever before.

37. 1.4 GENERATIONS OF COMPUTERS • Fourth Generation (Early 1970s–Till Date)—Microprocessors • Fourth-generation computers became more powerful, compact, reliable and affordable. As a result, it gave rise to the personal computer (PC) revolution. • The development of secondary memories such as hard disks became economical, smaller, and bigger in capacity. • The other significant development of this era was that these computers could be linked together to form networks, which eventually led to the development of the Internet.

38. 1.4 GENERATIONS OF COMPUTERS • Fourth Generation (Early 1970s–Till Date)—Microprocessors • This generation also saw the development of graphical user interfaces (GUIs), mouse and hand-held devices. • Despite many advantages, there is only one disadvantage of this generation, that is, it required complex and sophisticated technology for the manufacturing of CPU and other components. • Examples: Apple II, Altair 8800 and CRAY-1.

39. 1.4 GENERATIONS OF COMPUTERS • Fifth Generation (Present and Beyond)—Artificial Intelligence • The dream of creating a human-like computer that would be capable of reasoning and reaching at a decision through a series of 'what-if-then' analyses has existed since the beginning of computer technology. • Such a computer would learn from its mistakes and possess the skill of experts. • These are the objectives for creating the fifth-generation computers.

40. 1.4 GENERATIONS OF COMPUTERS • Fifth Generation (Present and Beyond)—Artificial Intelligence • The process of developing fifth-generation computers is still in the development stage, however three characteristics can be identified with the fifth-generation computers: • Mega Chips: Will result in the production of microprocessor having millions of electronic components on a single chip. • Parallel Processing: Will use multiple processors and perform parallel processing, thereby accessing several instructions at one time and working on them at the same time. • Artificial Intelligence (AI): It refers to a series of related technologies that tries to simulate and reproduce human behavior including thinking, speaking and reasoning. AI comprises a group of related technologies: expert systems (ES), natural language processing (NLP), speech recognition, vision recognition and robotics.

41. 1.5 CLASSIFICATION OF COMPUTERS • Computers are available in different sizes and types. Some computers are designed to be used by a single user only, whereas some computers can handle the needs of many users simultaneously. Computers also differ based on their data-processing abilities. In general, the computers can be classified according to purpose, data handling and functionality.

42. 1.5 CLASSIFICATION OF COMPUTERS • Classification According to Purpose • General-purpose Computers • A general-purpose computer is designed to perform a range of tasks. These computers have the ability to store numerous programs. Even though such computers are versatile, they generally lack in speed and efficiency. The computers used in schools and homes are general-purpose computers. • Specific-purpose Computers • These computers are designed to handle a specific problem or to perform a single specific task. A set of instructions for the specific task is built into the machine. Hence, they cannot be used for other applications unless their circuits are redesigned, that is, they lack versatility. These computers are used for airline reservations, satellite tracking and air traffic control.

43. 1.5 CLASSIFICATION OF COMPUTERS • Classification According to Type of Data-handling Techniques • Analog Computers • A computing machine that operates on data in the form of continuously variable physical quantities is known as analog computer. These computers do not deal directly with the numbers. They measure continuous physical magnitudes (e.g. temperature, pressure and voltage). For example, a gas pump may have an analog computer that converts the flow of pumped gas into two measurements: the quantity of petrol and the price of that quantity. • Analog computers are used for scientific and engineering purposes. One of the characteristics of these computers is that they give approximate results since they deal with quantities that vary continuously. The main feature of analog computers is that they are very fast in operation as all the calculations are done in 'parallel mode'.

44. 1.5 CLASSIFICATION OF COMPUTERS • Classification According to Type of Data-handling Techniques • Digital Computers • A computer that operates with information, numerical or otherwise, represented in a digital form is known as digital computer. Such computers process data (including text, sound, graphics and video) into a digital value (in 0s and 1s). In digital computers, analog quantities must be converted into digital quantity before processing. • Digital computers can give the results with more accuracy and at a faster rate. The accuracy of such computers is limited only by the size of their registers and memory. The desktop PC is a classic example of digital computer.

45. 1.5 CLASSIFICATION OF COMPUTERS • Classification According to Type of Data-handling Techniques • Digital Computers • A computer that operates with information, numerical or otherwise, represented in a digital form is known as digital computer. Such computers process data (including text, sound, graphics and video) into a digital value (in 0s and 1s). In digital computers, analog quantities must be converted into digital quantity before processing. • Digital computers can give the results with more accuracy and at a faster rate. The accuracy of such computers is limited only by the size of their registers and memory. The desktop PC is a classic example of digital computer.

46. 1.5 CLASSIFICATION OF COMPUTERS • Classification According to Functionality • Based on physical size, performance and application areas, the computers are generally classified into four major categories: micro, mini, mainframe and super computers.

47. 1.5 CLASSIFICATION OF COMPUTERS • Classification According to Functionality • Micro Computers • A micro computer is a small, low-cost digital computer, which usually consists of a microprocessor, a storage unit, an input channel and an output channel. The addition of a power supply and connecting cables, appropriate peripherals (keyboard, monitor, printer, disk drives and others), an operating system and other software programs can provide a complete micro computer system. • Originally, these computers were designed only for individual users, but nowadays they have become powerful tools for many businesses that, when networked together, can serve more than one user. Micro computers include desktop, laptop and hand-held models such as personal digital assistants (PDAs).

48. 1.5 CLASSIFICATION OF COMPUTERS • Classification According to Functionality • Micro Computers Hand-held Laptop Desktop

49. 1.5 CLASSIFICATION OF COMPUTERS • Classification According to Functionality • Micro Computers • Desktop Computer: A desktop computer or personal computer (PC) is principally intended for stand-alone use by an individual. The major criterion behind the importance of the PCs is that they are not very expensive for the individuals or for the small businesses. • Laptop: A laptop is a portable computer that a user can carry around. They are small computers enclosing all the basic features of a normal desktop computer. The biggest advantage of laptops is that they are lightweight and can be used anywhere and at any time, especially while traveling. Moreover, they do not need any external power supply as a rechargeable battery is completely self-contained. However, they are expensive as compared to desktop computers.

50. 1.5 CLASSIFICATION OF COMPUTERS • Classification According to Functionality • Micro Computers • Hand-held Computers: A hand-held computer such as PDA is a portable computer that can be conveniently stored in a pocket and used while the user is holding it. PDAs are essentially small portable computers and are slightly bigger than the common calculators. A PDA user generally uses a pen or electronic stylus, instead of a keyboard for input. • Hand-held computers usually have no disk drive; rather they use small cards to store programs and data. However, they can be connected to a printer or a disk drive to generate output or store data. They have limited memory and are less powerful as compared to desktop computers.