1

Computer Basics

1. Define ‘computer’. Explain some characteristics of computers.

Ans.: The term ‘computer’ is derived from the word ‘compute’, which means to calculate. A computer is an electronic machine, devised for performing calculations and controlling operations that can be expressed either in logical or numerical terms. In simple words, a computer is an electronic device that performs diverse operations with the help of instructions to process the data in order to achieve desired results. Although the application domain of a computer depends totally on human creativity and imagination, still it covers a huge area of applications including education, industries, government, medicine, scientific research, law, and even music and arts.

Today, much of the world's infrastructure runs on computers and it has profoundly changed our lives. Some of the characteristics of computers, which make them an essential part of every emerging technology, are described as follows:

	Speed: A computer processes data at an extremely fast rate, at millions or billions of instructions per second. It can perform a huge task in a few seconds that otherwise a normal human being may take days or even years to complete. The speed of a computer is calculated in megahertz (MHz), that is, one million instructions per second. At present, a powerful computer can perform billions of operations in just one second.
	Accuracy: Besides the efficiency, the computers are also very accurate. The level of accuracy depends on the instructions and the type of machines being used. Since the computer is capable of doing only what it is instructed to do, faulty instructions for data processing may lead to faulty results. This is known as GIGO (Garbage In Garbage Out). Thus, the probability of errors in computers is negligible.
	Diligence: The computer, being a machine, does not suffer from the human traits of tiredness and lack of concentration. If four million calculations have to be performed, then it will perform the last four-millionth calculation with the same accuracy and speed as the first calculation.
	Reliability: Generally, reliability is the measurement of the performance of a computer, which is measured against some predetermined standard for operation without any failure. The major reason behind the reliability of the computer is that, at hardware level, it does not require any human intervention between its processing operations. Moreover, it has built-in diagnostic capabilities, which help in continuous monitoring of the system.
	Storage capability: It can store large amounts of data and can recall the required information almost instantaneously. The main memory of the computer is relatively small and it can hold only a certain amount of data. Therefore, the data are stored on secondary storage devices such as magnetic tape or disks. Small sections of data can be accessed very quickly from these storage devices and brought into the main memory, as and when required, for processing.
	Versatility: It is quite versatile in nature. It can perform multiple tasks simultaneously with equal ease. For example, at one moment it can be used to draft a letter, another moment it can be used to play music, and in between one can print a document as well. All this work is possible by changing the program (computer instructions). Thus, it can perform various tasks by reducing the task to a series of logical steps.
	Resource sharing: In the initial stages of development, computer used to be an isolated machine. With the tremendous growth in computer technologies, it today has the capability to connect with each other. This has made the sharing of costly resources like printers possible. Apart from device sharing, data and information can also be shared among groups of computers, thus creating a large information and knowledge base.

2. Explain the brief history of the evolution of computers.

Ans.: The need for a device to do calculations along with the growth in commerce and other human activities explains the evolution of computers. Computer was preceded by many devices that mankind developed for their computing requirements. However, many centuries elapsed before technology was adequately advanced to develop computers. Some of the ancient time devices that led to the evolution of computers are as follows:

Sand Tables

In ancient times, people used fingers to perform calculations such as addition and subtraction. Even today, simple calculations are done on fingers. 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. A sand table consists of 3 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 1 pebble was added to the adjacent left groove. Afterward, sand tables were modified extensively and these modifications resulted in a device known as Abacus.

Abacus

It emerged around 5000 years ago in Asia Minor and in some parts of the world, it is still in use. The word ‘abacus’ was derived from the Arabic word ‘abaq’ which means ‘dust’. An abacus consists of sliding beads arranged on a rack, which has two parts—namely, upper and lower. The upper part contains two beads and lower part contains five beads per wire. The numbers are represented by the position of the beads on the rack. For example, in the upper part of the rack, a raised bead denotes 0 whereas a lowered bead denotes digit 5. In the lower part, a raised bead stands for 1 and a lowered bead for 0. The arithmetic operations like addition and subtraction can be performed by positioning the beads appropriately.

Napier Bones

In 1614, John Napier, a Scottish mathematician, made a more sophisticated computing machine called Napier bones. This was a small instrument made of 10 rods, on which the multiplication table was engraved. It was made of the strips of ivory bones, and so the name Napier bones. This device enabled the multiplication in a fast manner, if one of the numbers was of one digit only (e.g., 6 × 6745). Incidentally, Napier also played a key role in the development of logarithms, which stimulated the invention of slide rule, which substituted the addition of logarithms for multiplication. This was a remarkable invention as it enabled to perform the multiplication and division operations by converting them into simple addition and subtraction.

Slide Rule

The invention of logarithms influenced the development of another famous invention known as slide rule. In 1620 AD, the first slide rule came into existence. It was jointly devised by two British mathematicians, Edmund Gunter and William Oughtred. 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. It is embodied by the two sets of scales that are joined together, with a marginal space between them. This space is enough for the free movement of the slide in the groove of the rule. The suitable alliance of two scales enabled the slide rule to perform multiplication and division by a method of addition and subtraction.

Pascaline

In 1623, Wilhelm Schickard invented the calculating clock, which could add and subtract, and indicated the overflow by ringing a bell. Subsequently, it helped in the evolution of 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. It was operated by a series of dials attached to wheels with each wheel having 10 segments (numbered from 0 to 9) on its circumference. When a wheel made a complete turn, the wheel on its left advanced by one segment. Indicators above the dial displayed the correct answer. However, the usage of this device was limited to addition and subtraction only.

Analytical Engine

It is considered to be the first general-purpose programmable computer. 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. This was the fundamental difference between the analytical engine and the difference engine. Lady Ada Lovelace helped him in the development of the analytical engine. She not only helped Babbage with financial aid but also, being a good mathematician, wrote articles and programs for the proposed machine. Due to her contributions, she is known as the first programmer. However, Babbage never completed the analytical engine, but his proposal for this device reviewed the basic elements of modern computer such as input/output, storage, processor, and control unit.

Hollerith's Tabulator

Herman Hollerith invented the punched-card tabulating machine to process the data collected in the US Census. This electronic machine was able to read the information on the cards and process it electronically. It consisted of a tabulator, a sorter with compartments electronically controlled by the tabulator's counter, and the device used to punch data onto cards. It could read the presence or absence of holes in the cards by using spring-mounted nails that passed through the holes to make electrical connections. In 1896, Hollerith founded the Tabulating Machine Company, which was later named International Business Machines (IBM).

3. Explain the various well-known early computers, which are considered to be predecessors of modern computers.

Ans.: Some of the well-known computers of the past, which are considered to be predecessors of modern computers, are described as follows:

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. This electronic calculating machine used relays and electromagnetic components to replace mechanical components. It 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).

ABC

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. By the end of 1939, they built the first electronic computer named as ABC (Atansoft Berry Computer). It is considered as the first computing machine that introduced the idea of binary arithmetic, regenerative memory, and logic circuits. It used electronic vacuum tubes and the circuitry was based on George Boole's Boolean algebra.

Colossus

In 1944, Alan Mathison Turing, a British mathematician, along with some colleagues created a computer named colossus, which comprised 1800 vacuum tubes. It was one of the world's earliest working programmable electronic digital computers. It was a special-purpose machine that suited a narrow range of tasks (e.g., it was not capable of performing decimal multiplications). Although it was built as a special-purpose computer, it proved flexible enough to be programmed to execute a variety of different routines.

ENIAC

In 1946, John Eckert and John Mauchly of the Moore School of Engineering at the University of Pennsylvania developed ENIAC (Electronic Numerical Integrator and Calculator). Like the ABC, ENIAC also used electronic vacuum tubes for its internal parts. It embodied almost all the components and concepts of today's high-speed, electronic digital computers. It could discriminate the sign of a number, compare quantities for equality, add, subtract, multiply, divide, and extract square roots. It consisted of 18,000 vacuum tubes, required around 160 kW of electricity and weighed nearly 30 tons. It could compute at speeds 1000 times that of Mark-I but had a limited amount of space to store and manipulate information.

EDVAC

John Eckert and John Mauchly also proposed the development of EDVAC (Electronic Discrete Variable Automatic Computer). Although, the conceptual design for EDVAC was completed by 1946, it came into existence in 1949. It was the first electronic computer to use the stored program concept introduced by John Von Neumann and thus also known as Von-Neumann machine. It also had the capability of conditional transfer of control—that is, the computer could stop any time and then resumed again. It contained approximately 4000 vacuum tubes and 10,000 crystal diodes.

EDSAC

EDSAC (Electronic Delay Storage Automatic Calculator) was also based on John Von Neumann's stored program concept. The work began on EDSAC in 1946 at the Cambridge University by a team headed by Maurice Wilkes. In 1949, the first successful program was run on this machine. It used mercury delay lines for memory and vacuum tubes for logic. It had 3000 vacuum valves arranged on 12 racks and used tubes filled with mercury for memory. It could carry out only 650 instructions/s. A program was fed into the machine via a sequence of holes punched into a paper tape. It occupied a room, which measured 5 m × 4 m.

UNIVAC

UNIVAC (Universal Automatic Computer) was the first commercially available electronic computer. It was also the first general-purpose computer that was designed to handle both numeric and textual information. The Eckert–Mauchly Corporation manufactured it in 1951 and its implementation marked the real beginning of the computer era. UNIVAC could compute at a speed of 120–3600 μs. Magnetic tapes were used as input and output mediums at a speed of around 13,000 characters/s. It was 25 ft × 50 ft in length, contained 5600 tubes, 18,000 crystal diodes, and 300 relays. It was used for general-purpose computing with large amounts of input and output.

4. Explain about the generations of computers.

Ans.: The history of computer development is often discussed with reference to the different generations of computing devices. In computer terminology, the word ‘generation’ is described as a stage of technological development or innovation. A major technological development that fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper, and more powerful and more efficient and reliable devices characterize each generation of computer. According to the type of processor installed in a machine, there are five generations of computers.

First Generation (1940–56): Vacuum Tubes

They were vacuum tubes/thermionic valves-based machines. These computers used 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.

They relied on binary-coded language also called machine language (language of 0’s and 1’s) to perform operations and were able to solve only one problem at a time. Each machine was fed with different binary codes and hence were difficult to program. This resulted in lack of versatility and speed. In addition, to run on different types of computers, instructions must be rewritten or recompiled. Some examples of first generation computers are ENIAC, EDVAC, and UNIVAC.

Some characteristics of first generation computers are as follows:

	These computers were based on vacuum tube technology.
	These were the fastest computing devices of their times (computation time was in milliseconds).
	These computers were very large and required a lot of space for installation.
	Since thousands of vacuum tubes were used, these generated a large amount of heat. Therefore, air conditioning was essential.
	These were non-portable and very slow equipments.
	These lacked in versatility and speed.
	These were very expensive to operate and used a large amount of electricity.
	These machines were unreliable and prone to frequent hardware failures. Hence, constant maintenance was required.
	Since machine language was used, these computers were difficult to program and use.
	Each individual component had to be assembled manually. Hence, commercial appeal of these computers was poor.

Second Generation (1956–63): Transistors

These computers used transistors, which were superior to vacuum tubes. A transistor is made up of semiconductor material like germanium and silicon. It usually has three leads and performs electrical functions such as voltage, current, or power amplification with low power requirements. Since transistor is a small device, the physical size of computers was greatly reduced. Computers became smaller, faster, cheaper, energy-efficient, and more reliable than their predecessors. In second generation computers, magnetic cores were used as primary memory and magnetic disks as secondary storage devices. However, they still relied on punched cards for input and printouts for output.

One of the major developments of this generation includes the progress from machine language to assembly language. Assembly language uses 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 in this period. Some examples of second generation computers are PDP-8 (Programmed Data Processor-8), IBM 1401, and IBM 7090.

Some characteristics of second generation computers are as follows:

	These machines were based on transistor technology.
	These were smaller as compared to the first generation computers.
	The computational time of these computers was reduced to microseconds from milliseconds.
	These were more reliable and less prone to hardware failure. Hence, they required less frequent maintenance.
	These were more portable and generated less amount of heat.
	Assembly language was used to program computers. Hence, programming became more time-efficient and less cumbersome.
	These computers still required air conditioning.
	Manual assembly of individual components into a functioning unit was still required.

Third Generation (1964 to Early 1970s): Integrated Circuits

The development of the integrated circuit was the trait of the third generation computers. An integrated circuit (also called an IC) consists of a single chip (usually silicon) with many components such as transistors and resistors fabricated on it. It replaced several individually wired transistors. This development made computers smaller in size, reliable, and efficient.

Instead of punched cards and printouts, users interacted with third generation computers through keyboards and monitors and interfaced with operating system. This allowed the device to run many different applications simultaneously with a central program that monitored the memory. For the first time, computers became accessible to mass audience because they were smaller and cheaper than their predecessors. Some examples of third generation computers are NCR 395 and B6500.

Some characteristics of third generation computers are as follows:

	These computers were based on IC technology.
	These were able to reduce computational time from microseconds to nanoseconds.
	These were easily portable and more reliable than the second generation computers.
	These devices consumed less power and generated less heat. In some cases, air conditioning was still required.
	The size of these computers was smaller as compared to previous generation computers.
	Since hardware rarely failed, the maintenance cost was quite low.
	Extensive use of high-level languages became possible.
	Manual assembling of individual components was not required, so it reduced the large requirement of labour and cost. However, highly sophisticated technologies were required for the manufacturing of IC chips.
	Commercial production became easier and cheaper.

Fourth Generation (Early 1970s Till Date): Microprocessors

The fourth generation is an extension of the third generation technology. Although, the technology of this generation is still based on the IC, these computers have been made readily available to us because of the development of the microprocessor (circuits containing millions of transistors). The Intel 4004 chip, which was developed in 1971, took the IC one step further by locating all the components of a computer (central processing unit [CPU], memory, and input and output controls) on a minuscule chip. A microprocessor is built onto a single piece of silicon, known as chip. It is about 0.5 cm along one side and no more than 0.05 cm thick.

These 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 the millions. This way computers became smaller and cheaper than ever before.

These computers became more powerful, compact, reliable, and affordable. As a result, they gave rise to the personal computer (PC) revolution. During this period, magnetic core memories were substituted by semiconductor memories, which resulted in faster random access main memories. Moreover, 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. This generation also saw the development of the graphical user interfaces (GUIs), mouse, and handheld devices. Despite many advantages, this generation required complex and sophisticated technology for the manufacturing of CPU and the other components. Some examples of fourth generation computers are Apple II, Altair 8800, and CRAY-1.

Some characteristics of fourth generation computers are as follows:

	These computers are microprocessor-based systems.
	These are very small in size.
	These are the cheapest among all the other generation computers.
	These are portable and quite reliable.
	These machines generate negligible amount of heat, hence they do not require air conditioning.
	Hardware failure is negligible so minimum maintenance is required.
	The production cost is very low.
	GUIs and pointing devices enabled users to learn to use the computer quickly.
	Interconnection of computers led to better communication and resource sharing.

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’ analyzes have 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 of computers. The starting point for these computers had been set in the early 1990s. The process of developing these computers is still in the development stage and is using the concept of expert system. The expert system is defined as a computer system that attempts to mimic the thought process and reasoning of experts in specific areas.

Some characteristics identified with the fifth generation computers are as follows:

	Mega chips: These computers will use super-large scale integrated (SLSI) chips, which will result in the production of microprocessor having millions of electronic components on a single chip. In order to store instructions and information, these computers require a great amount of storage capacity. Mega chips may enable the computer to approximate the memory capacity of the human mind.
	Parallel processing: Computers with one processor that access and execute only one instruction at a time is called serial processing. However, these computers will use multiple processors and perform parallel processing thereby accessing several instructions at once 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 behaviour including thinking, speaking, and reasoning. It comprises a group of related technologies such as expert systems, natural language processing, speech recognition, vision recognition, and robotics.

5. Write the classification of computers according to purpose and data handling.

Ans.: These days, computers are available in many sizes and types. One can have a computer that can fit in the palm of the hand to those that can occupy the entire room. 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, they can be classified according to purpose, data handling, and functionality. But, here only two classifications of computers will be discussed.

Classification According to Purpose

Computers are designed for different purposes. According to the need, they can be classified into two categories as follows:

1. General-purpose computers: As the name suggests, they are designed to perform a range of tasks. These computers have the ability to store numerous programs. These machines can be used for various applications, ranging from scientific to business purpose applications. Even though such these computers are versatile, they generally lack in speed and efficiency. The computers that you use in your schools and homes are general-purpose computers.
2. Specific-purpose computers: They 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. However, being designed for specific tasks, they can provide the result very quickly and efficiently. These computers are used for airline reservations, satellite tracking, and air traffic control.

Classification According to Type of Data-handling Techniques

Different types of computers process the data in a different manner. According to the basic data-handling techniques, they can be classified into three categories as follows:

1. 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 (such as temperature, pressure, and voltage) that are analogous to the numbers under consideration. For example, the petrol pump may have an analog computer that converts the flow of pumped petrol into two measurements: the quantity of petrol and the price for that quantity. These 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 these computers is that they are very fast in operation as all the calculations are done in parallel mode. It is very easy to get graphical results directly using these computers. However, the accuracy of these computers is less.
2. 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 0’s and 1’s). In these computers, analog quantities must be converted into digital quantity before processing. In this case, the output will also be digital. If analog output is desired, the digital output has to be converted into analog quantity. The components, which perform these conversions, are the essential parts or peripherals of the digital computer. These 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 at the home is a classic example of digital computer.
3. Hybrid computers: They incorporated the measuring feature of an analog computer and counting feature of a digital computer. For computational purposes, these computers use the analog components and for the storage of intermediate results, digital memories are used. In order to bind the powers of analog and digital techniques, analog to digital and digital to analog, the hybrid computers comprehensively use converters. Such computers are broadly used for scientific applications, in various fields of engineering, and in industrial control processes.

6. Write the classification of computers according to functionality.

Ans.: Based on physical size, performance, and application areas, computers can be generally divided into four major categories: microcomputers, minicomputers, mainframe computers, and supercomputers.

Microcomputers

These are small, low-cost digital computers, which usually consist of a microprocessor, a storage unit, an input channel, and an output channel, all of which may be on one chip inserted into one or several PC boards. 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 microcomputer system. They are generally the smallest of the computer family. Originally, these were designed for individual users only, but nowadays they have become powerful tools for many businesses that, when networked together, can serve more than one user. IBM-PC Pentium 100, IBM-PC Pentium 200, and Apple Macintosh are some of the examples of microcomputers. They include desktop, laptop, and handheld models.

Minicomputers

In the early 1960s, Digital Equipment Corporation (DEC) started shipping its PDP series computer, which the press described and referred as minicomputers. A minicomputer is a small digital computer that normally is able to process and store less data than a mainframe but more than a microcomputer, while doing so less rapidly than a mainframe but more rapidly than a microcomputer. These computers are about the size of a two-drawer filing cabinet. Generally, they are used as desktop devices that are often connected to a mainframe in order to perform the auxiliary operations.

Minicomputers (sometimes called as mid-range computers) are designed to meet the computing needs of several people simultaneously in a small- to medium-sized business environment. They are capable of supporting from 4 to about 200 simultaneous users. They serve as a centralized storehouse for a cluster of workstations or as a network server. They are usually multi-user systems; so these are used in interactive applications in industries, research organizations, colleges, and universities. They are also used for real-time controls and engineering design work. Some of the widely used minicomputers are PDP 11, IBM (8000 series), and VAX 7500.

Mainframes

They are ultra-high performance computers made for high-volume, processor-intensive computing. They consist of high-end computer processors, with related peripheral devices, capable of supporting large volumes of data processing, high-performance online transaction processing, and extensive data storage and retrieval. Normally, they are able to process and store more data than a minicomputer and far more than a microcomputer. Moreover, they are designed to perform at a faster rate than a minicomputer and at even more faster rate than a microcomputer. They are the second largest (in capability and size) of the computer family, the largest being the supercomputers. However, they can usually execute many programs simultaneously at a high speed whereas supercomputers are designed for a single process.

Mainframes allow its user to maintain a large amount of data storage at a centralized location and to access and process this data from different computers located at different locations. They are typically used by large businesses and for scientific purposes. Some examples of mainframe are IBM's ES000, VAX 8000, and CDC 6600.

Supercomputers

These computers are the special purpose machines that are specially designed to maximize the numbers of FLOPS (floating point operation per second). Any computer below one gigaflop/s is not considered a supercomputer. They have the highest processing speed at a given time for solving scientific and engineering problems. Essentially, they contain a large number of CPUs that operate in parallel to make them faster. Their processing speed lies in the range of 400–10,000 MFLOPS (millions of floating point operation per second). Due to this feature, supercomputers help in many applications including information retrieval and computer-aided design.

They can process a great deal of data and make extensive calculations very quickly. They can resolve complex mathematical equations in a few hours, which would have taken many years when performed using a paper and pencil or using a hand calculator. They are the fastest, costliest, and most powerful computer available today. Typically, they are used to solve multi-variant mathematical problems of existent physical processes, such as aerodynamics, metrology, and plasma physics. They are also required by the military strategists to simulate defense scenarios. Cinematic specialists use them to produce sophisticated movie animations. Scientists build complex models and simulate them in a supercomputer. However, they have limited broad-spectrum use because of their price and limited market. The largest commercial uses of supercomputers are in the entertainment/advertising industry. CRAY-3, Cyber 205, and PARAM are some well-known supercomputers.

7. Write a short note on the following:

(a) Desktop computer

(b) Laptop

(c) Handheld computer

Ans.: (a) Desktop computer: It is also known as personal computer (PC). It is principally intended for stand-alone use by an individual. It is the most common type of microcomputer. This microcomputer typically consists of a system unit, a display monitor, a keyboard, internal hard disk storage, and other peripheral devices. The main reason behind the importance of the PC is that it is not very expensive for individuals or small businesses. Some of the major PC manufacturers are APPLE, IBM, Dell, and Hewlett-Packard.

(b) Laptop: It is a portable computer that a user can carry around. Since it resembles a notebook, it is also known as notebooks. It is a small computer enclosing all the basic features of a normal desktop computer. The biggest advantage of laptop is that it is lightweight and one can use it anywhere and at anytime, especially when one is travelling. Moreover, it does not need any external power supply as a rechargeable battery is completely self-contained. However, it is expensive as compared to desktop computers.

(c) Handheld computer: It is also called a personal digital assistant (PDA). It is a portable computer that can conveniently be stored in a pocket (of sufficient size) and used while the user is holding it. It is essentially a small portable computer and is slightly bigger than the common calculators. A PDA user generally uses a pen or electronic stylus, instead of a keyboard for input. The monitor is very small and is the only apparent form of output. Since these computers can be easily fitted on the top of the palm, they are also known as palmtop computer. It usually has no disk drive rather it uses small cards to store programs and data. However, it can be connected to a printer or a disk drive to generate output or store data. It has limited memory and is less powerful as compared to desktop computers. Some examples of handheld computers are Apple Newton, Casio Cassiopeia, and Franklin eBook Man.

8. Draw the block diagram of the digital computer and explain its various components.

Ans.: A computer can be viewed as a system, which consists of a number of interrelated components that work together with the aim of converting data into information. In a computer system, processing is carried out electronically, usually with little or no intervention from the user. Every computer needs to be instructed exactly what to do and how to do. The instructions given to computers are called programs. Without programs, computers would be useless. The physical parts that make up a computer (the CPU, input, output, and storage units) are known as hardware. Any hardware device connected to the computer or any part of the computer outside the CPU and working memory is known as a peripheral. Some examples of peripherals are keyboards, mouse, and monitors. There are several computer systems in the market with a wide variety of makes, models, and peripherals. In general, a computer system comprises of three components: central processing unit (CPU), input unit, and output unit. The block diagram of the digital computer is shown in Figure 1.1.

Figure 1.1 Block Diagram of a Digital Computer

CPU

CPU, also known as processor, is the brain of the computer system that processes data (input) and converts it into meaningful information (output). It is referred to as the administrative section of the computer system that interprets the data and instructions, coordinates the operations, and supervises the instructions. It works with data in discrete form, that is, either 1 or 0. It counts, lists, compares, and re-arranges the binary digits of data in accordance with the detailed program instructions stored within the memory. Eventually, the results of these operations are translated into characters, numbers, and symbols that can be understood by the user. The CPU itself has three parts which are described as follows:

1. Arithmetic logic unit (ALU): This unit performs the arithmetic (add, subtract) and logical operations (and, or) on the data made available to it. Whenever an arithmetic or logical operation is to be performed, the required data are transferred from the memory unit to ALU, the operation is performed, and the result is returned to the memory unit. Before the completion of the processing, data may need to be transferred back and forth several times between these two sections. Subsequently, the results are transferred from internal storage to an output device.
2. Control unit: This unit checks the correctness of the sequence of operations. It fetches the program instructions from the memory unit, interprets them, and ensures correct execution of the program. It also controls the input/output devices and directs the overall functioning of the other units of the computer.
3. Registers: These are the special-purpose, high-speed temporary memory units that can hold varied information such as data, instructions, addresses, and intermediate results of calculations. Essentially, they hold the information that the CPU is currently working on. They can be considered as the CPU's working memory, an additional storage location that provides the advantage of speed.

Input, Output, and Storage Units

The user must enter instructions and data into the computer system before any operation can be performed on the given data. Similarly, after processing the data, the information must go out from the computer system to the user. For this, every computer system incorporates input and output units that serve as a communication media between the computer system and the user.

An input unit accepts instructions and data from the user with the help of input devices such as keyboard, mouse, and light pen. Since the data and instructions entered through different input devices will be in different form, the input unit converts them into the form that the computer can understand. After this, it supplies the converted instructions and data to the computer for further processing.

An output unit performs just opposite to that of the input unit. It accepts the outputs (which are in machine-coded form) produced by the computer, converts them into the user understandable form, and supplies the converted results to the user with the help of output devices such as printer, monitor, and plotter.

Besides, a computer system incorporates the storage unit to store the input entered through the input unit before processing starts and to store the results produced by the computer before supplying them to the output unit. The storage unit of a computer comprises two types of memory/storage: primary and secondary. The primary memory (also called main memory) is the part of a computer that holds the instructions and data currently being processed by the CPU, the intermediate results produced during the course of calculations, and the recently processed data. While the instructions and data remain in main memory, the CPU can access them directly and quickly. However, it is quite expensive and has a limited storage capacity. Due to the limited size of primary memory, a computer employs secondary memory, which is extensively used for storing data and instructions. It supplies the stored information to other units of the computer as and when required. It is less expensive and has higher storage capacity than the primary memory. Some commonly used secondary storage devices are floppy disks, hard disks, and tape drives.

9. Explain the working of computer with block diagram.

Ans.: A task is assigned to the computer in a set of step-by-step instructions, which is known as program. These instructions tell the computer what to do with the input in order to produce the required output. To complete any task, the computer performs the following three basic steps (Figure 1.2):

1. Accepts input: Computer input is whatever is entered or fed into a computer system. It can be supplied by the user (such as by using a keyboard) or by another computer or device (such as a diskette or CD-ROM). Some examples of input include the words and symbols in a document, numbers for a calculation, and instructions for completing a process.
2. Processes the data: During this stage, the computer follows the instructions using the data that has been input. Examples of processing include calculations, sorting lists of words or numbers, and modifying documents according to user instructions.
3. Produces output: Computer output is the information that has been produced by a computer. Some examples of computer output include reports, documents, and graphs. It can be in several different formats, such as printouts or displayed on the screen.

Figure 1.2 Basic Computer Operations

10. What are the various applications of a computer?

Ans.: In the last few decades, computer technology has revolutionized businesses and other aspects of human life all over the world. Practically, every company, large or small, is now directly or indirectly dependent on computers for data processing. Computer systems also help in the efficient operations of railway and airway reservations, hospital records, accounts, electronic banking, and so on. Computers not only save time, but also save paper work. Some of the areas where computers are being used are listed as follows:

	Science: Scientists have been using computers to develop theories, to analyze, and to test the data. The fast speed and the accuracy of the computer allow different scientific analyzes to be carried out. They can be used to generate detailed studies of how earthquakes affect buildings or pollution affects weather pattern. Satellite-based applications have not been possible without the use of computers. It would also not be possible to get the information of our solar system and the cosmos without computers.
	Education: They have also revolutionized the whole process of education. Currently, classrooms, libraries, and museums are utilizing computers to make the education much more interesting. Unlike recorded television shows, computer-aided education and computer-based training packages are making learning much more interactive.
	Medicine and health care: There has been an increasing use of computers in the field of medicine. Now, doctors are using computers right from diagnosing the illness to monitoring a patient's status during complex surgery. By using automated imaging techniques, doctors are able to look inside a person's body and can study each organ in detail (such as CAT scans or MRI scans), which was not possible few years ago. There are several examples of special-purpose computers that can operate within the human body such as a cochlear implant, a special kind of hearing aid that makes it possible for deaf people to hear.
	Engineering/Architecture/Manufacturing: Architects and engineers are extensively using computers in designing and drawings. Computers can create objects that can be viewed from all three dimensions. By using techniques like virtual reality, architects can explore houses that have been designed but not built. The manufacturing factories are using computerized robotic arms in order to perform hazardous jobs. Besides, computer-aided manufacturing can be used in designing the product, ordering the parts, and planning production. Thus, computers help in co-coordinating the entire manufacturing process.
	Entertainment: Computers are finding greater use in the entertainment industry. They are used to control images and sounds. The special effects, which mesmerize the audience, would not have been possible without computers. In addition, computerized animation and colourful graphics have modernized the film industry.
	Communication: E-mail or electronic mail is one of the communication media in which computer is used. Through e-mail, messages and reports are passed from one person to one or more persons with the aid of computer and telephone line. The advantage of this service is that while transferring the messages it saves time, avoids wastage of paper, and so on. Moreover, the person who is receiving the messages can read the messages whenever he is free and can save it, reply to it, forward it, or delete it from the computer.
	Business application: This is one of the important uses of the computer. Initially, computers were used for batch processing jobs, where one does not require the immediate response from the computer. Currently, they are mainly used for real-time applications (like at the sales counter) that require immediate response from the computer. There are various concerns for which computers are used such as in business forecasting, to prepare pay bills and personal records, in banking operations and data storage, in various types of life insurance business, and as an aid to management. Businesses are also using the networking of computers, where a number of computers are connected together to share the data and the information. Use of e-mail and Internet has changed the ways of doing business.
	Publishing: Computers have created a field known as desktop publishing (DTP). In DTP, with the help of the computer and a laser printer one can perform the publishing job all by oneself. Many of the tasks requiring long manual hours such as making table of contents and index can be automatically performed using computers and DTP software.

11. What are the various computerized activities in banks?

Ans.: Computers are extensively used in the field of banking and finance. They help in saving time to process customer's queries and are useful in tracking certain transactions. Thus, various computerized related activities in banks are as follows:

	When different branches of the bank are connected through computer networks, the inter-branch transactions such as cheque and draft can be performed by the computers without any delay.
	Banks use computers to track customer information such as name, address, phone number, date of birth, social security number, and place of employment. This information is used to stay in touch with customers and notify them of any changes in bank policy.
	They can store list of products and services availed by a customer. Thus, enabling bank personnel to periodically call customers for offering them a product or service such as home equity line of credit.
	With a computer, banks can analyze aging reports and track customers who have cheques returned due to non-sufficient funds. Moreover, computers can be used to track customers who are overdue on their loan and credit card payments.
	They help to keep a record of all transactions for the day. When customers make deposits and withdrawals or apply for mortgage loans, a computer will store and track all the information once a bank employee keys it into the system.
	A bank can use computers for new loan applications, credit card applications, and opening new accounts.
	A bank can also use a computer to see which safety deposit boxes are available and, thus, can keep a record of customers who have safety deposit boxes.

12. Discuss the applications of computers in defence.

Ans.: Computers are widely used for military applications for which sophisticated software has been developed. Computers and software are and have been used to enhance the defence of nations, businesses, and networks. Therefore, widely used applications of computers in defence are as follows:

	Computers are used in the development of ballistic missiles. Ballistic missiles are used to destroy targets far from the originating country. Global positioning system (GPS) is used to guide the ballistic missiles to the target. There are a number of satellites that help in determining the position of the missile and the target. The military uses GPS to track location of enemy.
	Smart bombs are guided by the software to the intended target. This ensures the precision and accuracy of the bombs.
	Communications play a critical role in military applications. The software encrypts the communication so that the enemy cannot decrypt the messages. Sophisticated algorithms are used in the encryption process.
	Supercomputers are being used by many nations in the area of defence.
	The military displays and computers are being used for mission-critical defence applications. These systems increase reliability and can be used indoors or outdoors in direct sunlight at extreme temperatures.
	Some other applications of computers in defence include propulsion control systems, fire sensor systems, engine control, bridge wing display units, and shaft alley monitoring systems.

13. Discuss the limitations of computers.

Ans.: Although computers are widely used in various fields, but still they have some limitations. They are as follows:

	Computers are faster, more diligent, accurate, and versatile than human beings but they cannot replace them. Thus, one can say that they do not have any intelligence.
	They can only perform what they are programmed to do. They work only on stored procedures and cannot think for themselves. Thus, they cannot make any decisions of their own.
	They need well-defined instructions to perform any operation. Therefore, they are unable to give any conclusion without going through intermediate steps and thus cannot generate information on their own.
	Their use is limited in areas where qualitative considerations are important. For instance, they can make plans based on situations and information but they cannot foresee whether they will succeed or not.
	They cannot correct wrong instructions. If the instructions are not accurate then the working of the computer will not be accurate. Therefore, they will give wrong information if feeded with wrong data.
	They need to be installed in a dust-free place. As some parts of computers get heated up due to heavy processing, the ambient temperature of system should be maintained.
	Computer parts require regular checking and maintenance in order to give correct result. This is because sometimes a program that was running correctly for some period of time produces an error when re-run later.

Multiple-choice Questions

1.  Analytical engine was developed by ____________.

(a) Gottfried Wilhelm von Leibniz

(b) Charles Babbage

(c) Herman Hollerith

(d) Joseph-Marie Jacquard

2.  The development of computers can be divided into ____________ generations.

(a) 3

(b) 4

(c) 5

(d) 6

3.  UNIVAC is an example of ____________.

(a) First generation computer

(b) Second generation computer

(c) Third generation computer

(d) Fourth generation computer

4.  The main distinguishing feature of fifth generation computers will be ____________.

(a) Liberal use of microprocessors

(b) Artificial intelligence

(c) Extremely low cost

(d) Versatility

5.  Find the odd one out.

(a) Microcomputer

(b) Minicomputer

(c) Supercomputer

(d) Digital computer

6.  The computer that is not considered as a portable computer is ____________.

(a) Laptop

(b) PDA

(c) Minicomputer

(d) None of these

7.  ____________ is a very small computer that can be held in the palm of the hand.

(a) PDA

(b) PC

(c) Laptop

(d) Minicomputer

8.  CPU stands for ____________.

(a) Central protection unit

(b) Central processing unit

(c) Central power unit

(d) Central prerogative unit

9.  The ____________ is the administrative section of the computer system.

(a) Input unit

(b) Output unit

(c) Memory unit

(d) Central processing unit

10.  The unit that performs the arithmetic and logical operations on the stored numbers is known as ____________.

(a) Arithmetic logic unit

(b) Control unit

(c) Memory unit

(d) Both (a) and (b)

Answers

1. (b)

2. (c)

3. (a)

4. (b)

5. (d)

6. (c)

7. (a)

8. (b)

9. (d)

10. (a)