Fundamentals of Computers PDF

FUNDAMENTALS OF COMPUTERS ABOUT THE AUTHOR E Balagurusamy, former Vice Chancellor, Anna University, Chennai, is currently Member, Union Public Service Commission, New Delhi. He is a teacher, trainer, and consultant in the ﬁelds of Information Technology and Management. He holds an ME (Hons) in Electrical Engineering and PhD in Systems Engineering from the Indian Institute of Technology, Roorkee. His areas of interest include Object-Oriented Software Engineering, Electronic Business, Technology Management, Business Process Re-engineering, and Total Quality Management. A proliﬁc writer, he has authored a large number of research papers and several books. His best selling books, among others, include: ∑ Programming in C#, 2e ∑ Programming in Java, 3e ∑ Programming in ANSI C, 4e ∑ Object-Oriented Programming with C++, 4e ∑ Programming in BASIC, 3e ∑ Numerical Methods ∑ Reliability Engineering A recipient of numerous honours and awards, he has been listed in the Directory of Who’s Who of Intellectuals and in the Directory of Distinguished Leaders in Education. FUNDAMENTALS OF COMPUTERS E Balagurusamy Member Union Public Service Commission Tata McGraw Hill Education Private Limited NEW DELHI McGraw-Hill Ofﬁces New Delhi New York St Louis San Francisco Auckland Bogotá Caracas Kuala Lumpur Lisbon London Madrid Mexico City Milan Montreal San Juan Santiago Singapore Sydney Tokyo Toronto Published by the Tata McGraw Hill Publishing Company Limited, 7 West Patel Nagar, New Delhi 110 008. Fundamentals of Computers Copyright © 2009 by Tata McGraw Hill Publishing Company Limited. No part of this publication may be reproduced or distributed in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise or stored in a database or retrieval system without the prior written permission of the publishers. The program listing (if any) may be entered, stored and executed in a computer system, but they may not be reproduced for publication. This edition can be exported from India only by the publishers, Tata McGraw Hill Publishing Company Limited. ISBN 13: 978-0-07-014160-5 ISBN 10: 0-07-014160-6 Managing Director: Ajay Shukla General Manager: Publishing—SEM & Tech Ed: Vibha Mahajan Manager—Sponsoring: Shalini Jha Associate Sponsoring Editor: Nilanjan Chakravarty Editorial Executive: Tina Jajoriya Development Editor: Surbhi Suman Jr. Executive—Editorial Services: Dipika Dey Sr. Production Executive: Suneeta S Bohra General Manager: Marketing—Higher Education & School: Michael J Cruz Sr. Product Manager: SEM & Tech Ed: Biju Ganesan General Manager—Production: Rajender P Ghansela Asst. General Manager—Production: B L Dogra Information contained in this work has been obtained by Tata McGraw Hill, from sources believed to be reliable. However, neither Tata McGraw Hill nor its authors guarantee the accuracy or completeness of any information published herein, and neither Tata McGraw Hill nor its authors shall be responsible for any errors, omissions, or damages arising out of use of this information. This work is published with the understanding that Tata McGraw Hill and its authors are supplying information but are not attempting to render engineering or other professional services. If such services are required, the assistance of an appropriate professional should be sought. Published by the Tata McGraw Hill Publishing Company Limited, 7 West Patel Nagar, New Delhi 110 008, typeset at Bukprint India, B-180A, Guru Nanak Pura, Laxmi Nagar-110 092 and printed at Gopsons, A-2 & 3, Sector-64, Noida 201 301 RYLCRRAFRQRXQ PREFACE We live in a technology-driven world, where almost everything is automated. The last two decades have seen a renaissance in the world of innovations. We have seen doctors perform surgery by sitting miles away from their patients. The fashion industry is soon to replace supermodels with robots (one such, the HRP-4C, was recently unveiled in Tokyo). There are similar advances being made in every ﬁeld, all of whose foundations are based on computers. It can often be perplexing for a beginner to keep pace with such developments. To be lost in the world of codes and bytes can be nerve-racking. And this is where a text book of this nature comes in. Written assuming absolutely no prior knowledge of computers, this book carries the reader through the world of Computers in a simple and structured manner. There are certain things that this book achieves and some it doesn’t. If you are looking for an exhaustive discussion on topics like DBMS and Computer Networks, this book is not meant for you. I would rather have you pick up books written by a Forouzan or a Gehrke. This book will not make you go through miles of C programming codes. So, if you want a good discussion on C implementation, I would rather have you pick my ANSI C book. What this book does aim to achieve is to give you an eye opener, a mild introduction, to the fascinating world of Computers. It will show you the basic building blocks of a computer, how they interact among each other, what are the various input and output devices and how a computer interprets and understands your language. It also gives an introduction to the various software that are popularly used on desktop computers. Seeing the importance of programming in today’s world, I have also provided a chapter on C programming, which serves as an introduction to this amazingly powerful language. There indeed are several books that ﬂood local book shops on this subject. So why should you use this one? The answer is simple; I haven’t written this book keeping a speciﬁc audience in mind. Whether you are a school student, a budding engineer pursuing technical education, or simply an inquisitive being in search of an appropriate introduction to computers, chances are I have kept all your requirements in mind while writing. I have kept the language at a level that can be accessed by one and all, and yet kept the discussions thorough and focused. More speciﬁcally, it can be used by the following: ∑ Students pursuing DCA, BSc (IT), BCA, MCA, MSc (IT), DOEACC ‘O’ Level courses ∑ Students pursuing ﬁrst-year engineering course in computers ∑ Students pursuing BBA, MBA and MCM courses ∑ Students pursuing short-term courses in various IT training institutes ∑ Self-learners for acquiring knowledge on various computer components, be it software or hardware. Finally, this book is for everyone who is either excited about computers or interested in knowing more about computers. This book is impregnated with several salient features: ∑ A complete self-study material for obtaining basic knowledge and understanding of various hardware and software components of computers. ∑ Covers Microsoft Ofﬁce suite of software such as MS Word and MS Excel in great detail. ∑ Concepts are explained using ample number of illustrations and screen shots for visualisation of the commands. vi Preface ∑ A chapter dedicated for further reading on Programming concepts. ∑ Appendices on Multimedia and Computer Graphics. The chapter organisation makes way for an easy graduation of topics from the very basic to seemingly complicated aspects of Computers. The ﬁrst nine chapters elaborate the fundamentals of a computer system by delving on topics like Organisation, Architecture, Storage Systems, Computer Arithmetic, and Boolean Algebra. The next six chapters cover Software that we often use in our everyday life through chapters on Operating Systems, Database Management Systems, Computer Networks and Programming Languages. The concluding chapter on C Programming readies the reader to develop and implement C programs. ONLINE LEARNING CENTRE The accompanying web supplement to this book provides an additional resource for students and instructors. This domain is ﬁlled with entities like chapter wise PowerPoint slides, additional solved programming examples, and few case studies on C programming. ACKNOWLEDGEMENTS My sincere thanks are also due to the editorial and publishing professionals at Tata McGraw Hill for their keen interest and support in bringing out this book in record time. The readers of the book are encouraged to send their comments, queries and suggestions at the following email id—[email protected] (kindly mention the title and author name in the subject line). E Balagurusamy CONTENTS Preface v 1. Understanding the Computer 1 1.1 Introduction 1 1.2 Evolution of Computers 3 1.3 Generations of Computers 6 1.4 Classiﬁcation of Computers 11 1.5 Computing Concepts 18 1.6 The Computer System 18 1.7 Applications of Computers 20 Chapter Summary 21 Key Terms to Remember 21 Review Questions Fill in the blanks 22 Multiple Choice Questions 23 Discussion Questions 24 2. Computer Organisation and Architecture 26 2.1 Introduction 26 2.2 Central Processing Unit 27 2.3 Internal Communications 30 2.4 Machine Cycle 34 2.5 The Bus 35 2.6 Instruction Set 36 Chapter Summary 38 Key Terms to Remember 38 Review Questions Fill in the blanks 39 Multiple Choice Questions 40 Discussion Questions 41 3. Memory and Storage Systems 43 3.1 Introduction 43 3.2 Memory Representation 44 3.3 Random Access Memory 46 3.4 Read Only Memory 49 viii Contents 3.5 Storage Systems 50 3.6 Magnetic Storage Systems 50 3.7 Optical Storage Systems 53 3.8 Magneto Optical Systems 55 3.9 Solid-state Storage Devices 56 3.10 Storage Evaluaton Criteria 58 Chapter Summary 58 Key Terms to Remember 59 Review Questions Fill in the blanks 59 Multiple Choice Questions 60 Discussion Questions 61 4. Input Devices 63 4.1 Introduction 63 4.2 Keyboard 64 4.3 Pointing Devices 65 4.4 Scanning Devices 68 4.5 Optical Recognition Devices 70 4.6 Digital Camera 72 4.7 Voice Recognition System 74 4.8 Data Acquisition Sensors 74 4.9 Media Input Devices 74 Chapter Summary 76 Key Terms to Remember 76 Review Questions Fill in the blanks 77 Multiple Choice Questions 78 Discussion Questions 79 5. Output Devices 81 5.1 Introduction 81 5.2 Display Monitors 82 5.3 Printers 84 5.4 Impact Printers 84 5.5 Non-impact Printers 86 5.6 Plotters 87 5.7 Voice Output Systems 88 5.8 Projectors 89 5.9 Terminals 89 Chapter Summary 90 Key Terms to Remember 90 Contents ix Review Questions Fill in the blanks 91 Multiple Choice Questions 92 Discussion Questions 93 6. Computer Codes 94 6.1 Introduction 94 6.2 Decimal System 95 6.3 Binary System 96 6.4 Hexadecimal System 97 6.5 Octal System 98 6.6 4-bit Binary Coded Decimal (BCD) Systems 99 6.7 8-bit BCD Systems 103 6.8 16-bit Unicode 108 6.9 Conversion of Numbers 110 Chapter Summary 119 Key Terms to Remember 119 Review Questions Fill in the blanks 120 Multiple Choice Questions 121 Discussion Questions 122 7. Computer Arithmetic 123 7.1 Introduction 123 7.2 Binary Addition 124 7.3 Binary Multiplication 126 7.4 Binary Subtraction 128 7.5 Binary Division 130 7.6 Signed/unsigned Numbers 132 7.7 Complements of Binary Numbers 133 7.8 Binary Subtraction Using Complements 137 7.9 Representing Numbers 143 7.10 Integer Arithmetic 145 7.11 Floating-point Arithmetic 152 7.12 Errors in Arithmetic 154 7.13 Laws of Arithmetic 156 Chapter Summary 158 Key Terms to Remember 158 Review Questions Fill in the blanks 159 Multiple Choice Questions 159 Discussion Questions 161 x Contents 8. Boolean Algebra of Switching Circuits 162 8.1 Introduction 162 8.2 Elements of Boolean Algebra 163 8.3 Basic Postulates of Boolean Algebra 165 8.4 Boolean Operations 166 8.5 Principle of Duality 167 8.6 Basic Laws of Boolean Algebra 168 8.7 Demorgan’s Theorem 178 8.8 Boolean Expressions 180 8.9 Venn Diagram 182 Chapter Summary 184 Key Terms to Remember 184 Review Questions Fill in the blanks 185 Multiple Choice Questions 186 Discussion Questions 187 9. Logic Gates and Digital Circuits 189 9.1 Introduction 189 9.2 Basic Logic Gates 190 9.3 Derived Logic Gates 193 9.4 Conversion of Boolean Functions 195 9.5 Adder Circuits 202 9.6 Flip-ﬂop Circuits 204 9.7 Application of Flip-ﬂops 206 Chapter Summary 209 Key Terms to Remember 209 Review Questions Fill in the blanks 209 Multiple Choice Questions 210 Discussion Questions 211 10. Computer Software 213 10.1 Introduction 213 10.2 Types of Computer Software 214 10.3 System Management Programs 215 10.4 System Development Programs 217 10.5 Standard Application Programs 220 10.6 Unique Application Programs 223 10.7 Problem Solving 225 Contents xi 10.8 Structuring the Logic 228 10.9 Using the Computer 231 Chapter Summary 232 Key Terms to Remember 233 Review Questions Fill in the blanks 234 Multiple Choice Questions 234 Discussion Questions 235 11. Operating Systems 237 11.1 Introduction 238 11.2 History of Operating Systems 238 11.3 Functions of Operating Systems 239 11.4 Process Management 240 11.5 Memory Management 246 11.6 File Management 249 11.7 Device Management 251 11.8 Security Management 253 11.9 Types of Operating Systems 253 11.10 Providing User Interface 256 11.11 Popular Operating Systems 258 Chapter Summary 262 Key Terms to Remember 263 Review Questions Fill in the blanks 264 Multiple Choice Questions 265 Discussion Questions 266 12. Microsoft Software 267 12.1 Introduction 267 12.2 MS-DOS 268 12.3 MS Word System 278 12.4 MS Excel System 290 12.5 MS Powerpoint System 298 12.6 MS Access System 303 12.7 MS Publisher 319 Chapter Summary 327 Key Terms to Remember 328 Review Questions Fill in the blanks 329 Multiple Choice Questions 329 Discussion Questions 331 xii Contents 13. Programming Languages 332 13.1 Introduction 332 13.2 History of Programming Languages 333 13.3 Generations of Programming Languages 335 13.4 Characteristics of a Good Programming Language 340 13.5 Categorisation of High-level Languages 341 13.6 Popular High-level Languages 343 13.7 Factors Affecting the Choice of a Language 347 13.8 Developing a Program 348 13.9 Running a Program 351 Chapter Summary 352 Key Terms to Remember 352 Review Questions Fill in the blanks 353 Multiple Choice Questions 354 Discussion Questions 355 14. Data Communications and Networks 356 14.1 Introduction 356 14.2 Data Communication Using Modem 357 14.3 Computer Network 359 14.4 Network Topologies 365 14.5 Network Protocols and Software 369 14.6 Applications of Network 370 Chapter Summary 370 Key Terms to Remember 371 Review Questions Fill in the blanks 371 Multiple Choice Questions 372 Discussion Questions 373 15. The Internet and World Wide Web 375 15.1 Introduction 375 15.2 History of Internet 376 15.3 Internet Applications 378 15.4 Understanding the World Wide Web 381 15.5 Web Browsers 381 15.6 Browsing the internet 384 15.7 Using a Search Engine 386 15.8 Email Service 389 Contents xiii 15.9 Protocols Used for the Internet 389 Chapter Summary 392 Key Terms to Remember 392 Review Questions Fill in the blanks 393 Multiple Choice Questions 393 Discussion Questions 395 16. Introduction to C Programming 396 16.1 Introduction 396 16.2 Characer set, Keywords and Data Types 398 16.3 Preprocessor Directives 401 16.4 Constants and Variable Types 403 16.5 Operators and Statements 406 16.6 Control Statements 411 16.7 Arrays and Strings 432 16.8 Functions 434 16.9 Structures 439 16.10 Pointers 442 16.11 Files in C 443 Chapter Summary 445 Sample Programs 445 Key Terms to Remember 449 Review Questions Fill in the blanks 450 Multiple Choice Questions 451 Discussion Questions 452 Appendix A 453 Appendix B 460 WALKTHROUGH Chapter Objectives The objectives enable students to set tangible goals before they begin each chapter. Chapter Outline A listing of topic headings is provided for each chapter, to help students organise the material in their own minds. xvi Walkthrough 284 Fundamentals of Computers 66 Fundamentals of Computers Editing the document Editing a document generally involves the operations, such as selecting the ∑ Optical mouse An optical mouse is a pointing text, moving and copying the text and deleting either the selected text or the entire text in the document input device in which the reﬂected light determines the window. For selecting the text, say “This is my word”, in the mydoc document, we need to perform the movement of the cursor on the displayed screen. The following steps: upper portion of the optical mouse is similar to that of 1. Open the mydoc — Microsoft Word window. the mechanical mouse. The lower portion of the optical 2. Set the insertion point before the word “This” in the document window, as shown in Fig. 12.9. mouse consists of a ball having Light Emitting Diodes (LEDs), an optical sensor and a Digital Signal Processor (DSP). Figure 4.3 shows the lower portion of the optical mouse. Fig. 4.3 The lower portion of the optical mouse 4.3.2 Trackball Trackball is a pointing device that basically consists of a socket containing the ball, which can be rolled manually to move the cursor on the screen. The socket also contains sensors, which detect the movement of the ball. With the help of the trackball, we can change the position of the cursor on the screen by simply rotating the ball with our ﬁngers or thumb. On the basis of size, the trackballs are classiﬁed into two types, small trackball and large trackball. The small trackballs are commonly used in portable computers, whereas Fig. 4.4 The trackball on the desk the large trackballs ﬁnd their use in the desktop computer systems, which are used for computer-aided designing. One of the most important advantages of the trackball is that it can be placed on different surfaces, such as desk, mouse pad and even user’s hand. The trackball ﬁnds its Fig. 12.9 Placing the insertion point use as a game controller in games like Centipede, Golden Tee and Marble Madness. Figure 4.4 shows the trackball placed on a desk. 3. Press the left mouse button and drag the mouse pointer up to the desired level of the selection. 4. Release the left mouse button to complete the selection, as shown in Fig. 12.10. 4.3.3 Light Pen Light pen is an electro-optical pointing device that is used for selecting the objects on the display screen with the help of a light sensitive pen. It is generally connected to the Visual Display Unit (VDU) of the computer system. The pen contains a light-sensitive diode, which helps in pointing the objects displayed on the screen. Using a light pen, we can directly draw the objects on the screen by holding it in our hand. When the tip of the light pen is brought in contact with the screen, the light coming from the screen causes a pulse to be generated in the pen which in turn causes the processor to identify the position pointed to by the pen. Light pens provide all the capabilities of a mouse. They do not require any pad or Fig. 12.10 Selecting the desired text in the document window horizontal surface and therefore, are useful Note: We can select the entire content of the document by either selecting Edit Select All option or by when desk space is limited. Figure 4.5 shows pressing the Ctrl and A keys simultaneously. the light pen attached to a computer system. Fig. 4.5 The light pen Clear Illustrations Figures and Tables interspersed throughout the text, illustrate key concepts. Walkthrough xvii Introduction Each chapter opening section contains an introduction providing the students with an overview of the topics to be presented within the chapter. Chapter Summary Summary serves as an ideal mini- study guide, for reviewing the major concepts in the chapter prior to examinations. Key Terms to Remember Key terms give a list of the important words discussed in the chapter. xviii Walkthrough Review Questions Readers can assess their knowledge by answering Fill in the Blanks and Multiple Choice Questions, provided under the heading ‘Review Questions’ Discussion Questions Discussion questions, at the end of each chapter, allow a student to review the key concepts and assess his or her understanding. Walkthrough xix Solved Examples Provided at appropriate locations, solved examples aid in learning the technique of applying concepts to practical problems. Example 16.3 Write a program to determine whether the year entered by the user is a leap year or not. Solution: The following program determines whether the year is a leap year or not: #include #include void main() { int yr; clrscr(); printf(“Enter the year”); scanf(“%d”,&yr); if(yr%100==0) { if(yr%400==0) printf(“\n Year is leap year”); else } printf(“\n Year is not leap year”); Sample Programs else { if(yr%4==0) Chapter 16 on Introduction printf(“\n Leap year”); else printf(“\n Not a leap year”); to C Programming depicts } getch(); implementation of C pro- } In the above code, variable yr is taken as an integer data type that stores the value of the year entered by gramming concepts. the user. The nested if else statements are used to determine whether the year entered by the user is a leap year or not and the result is displayed on the screen by using the printf statement. Figure 16.11 shows the output of the above program. Fig. 16.11 Displaying the leap year xx Walkthrough Useful Appendices Appendix A and B provide useful information on Multimedia and Computer Graphics. C HA PTE R 1 UNDERSTANDING THE COMPUTER Chapter Outline Chapter Objectives 1.1 Introduction In this chapter, we will learn: 1.2 Evolution of Computers ∑ How computers receive, store and process 1.2.1 Manual Computing Devices data to generate useful information. 1.2.2 Automated Computing Devices ∑ The improvements in functioning of 1.3 Generations of Computers computers in the last few decades. ∑ The ﬁve generations of computers. 1.3.1 First Generation Computers ∑ How to classify computers on the basis of 1.3.2 Second Generation Computers operating principles, applications and size. 1.3.3 Third Generation Computers ∑ The computer system as a combination of 1.3.4 Fourth Generation Computers hardware, software, data and people. 1.3.5 Fifth Generation Computers ∑ The use of computers in different ﬁelds. 1.4 Classiﬁcation of Computers 1.4.1 Based on Operating Principles 1.4.2 Based on Applications 1.1 INTRODUCTION 1.4.3 Based on Size and Capability 1.5 The Computer System A computer is an electronic machine that takes input from the user, processes the given input and 1.5.1 Hardware generates output in the form of useful information. 1.5.2 Software A computer accepts input in different forms such as 1.5.3 Data data, programs and user reply. Data refer to the raw 1.5.4 People details that need to be processed to generate some 1.6 Computing Concepts useful information. Programs refer to the set of 1.7 Applications of Computers instructions that can be executed by the computer in sequential or non-sequential manner. User reply Chapter Summary is the input provided by the user in response to a Key Terms to Remember question asked by the computer. The main task of Review Questions a computer system is to process the given input Fill in the Blanks of any type in an efﬁcient manner. Therefore, Multiple Choice Questions computer is also known by various other names Discussion Questions such as data processing unit, data processor and data processing system. 2 Fundamentals of Computers A computer includes various devices that function as an integrated system to perform several tasks described above. These devices are: Central Processing Unit (CPU) It is the processor of the computer that is responsible for controlling and executing instructions in the computer. It is considered as the most signiﬁcant component of the computer. It is the “brain” of the computer. Monitor It is a screen, which displays information in visual form, after receiving the video signals from the computer. Keyboard and Mouse These are the devices, which are used by the computer, for receiving input from the user. Figure 1.1 shows the various components of a computer. The unique capabilities and characteristics of a computer have made it very popular among its various users, including engineers, managers, accountants, teachers, students, etc. The characteristics and capabilities of a modern digital computer include, among others: Speed A computer is a fast electronic device that can solve large and complex problems in few seconds. The speed of a computer generally depends upon its hardware conﬁguration. Fig. 1.1 The components of computer Storage capacity A computer can store huge amount of data in its different storage components in many different formats. The storage area of a computer system is generally divided into two categories, main memory and secondary storage. Accuracy A computer carries out calculations with great accuracy. The accuracy achieved by a computer depends upon its hardware conﬁguration and the instructions. Reliability A computer produces results with no error. Most of the errors generated in the computer are human errors that are created by the user itself. Therefore, they are very trustworthy machines. Versatility Computers are versatile machines. They can perform many different tasks and can be used for many different purposes. Diligence Computers can perform repetitive calculations any number of times with the same accuracy. Computers do not suffer from human traits, such as tiredness, fatigue, lack of concentration, etc. Although computers are highly reliable and versatile machines, they do possess certain limitations. Since computers are capable of doing only what they are instructed to do, any wrong instruction (or faulty logic) or any wrong data may result in erroneous output. This is popularly known as “Garbage-In, Garbage-Out” (GIGO). Computer is a dumb machine and therefore lacks “common sense”. Anything it does is a result of human instructions. It carries out instructions as long as it can understand them, no matter whether they are right or wrong. Although computers can be instructed to make certain decisions based on mathematical or logical equations, they cannot make decisions in situations where qualitative considerations are involved. Understanding the Computer 3 1.2 EVOLUTION OF COMPUTERS In ancient times, people used different devices and methods for performing the computing operations. However, these devices and methods used for calculations were not very fast and accurate. This fact had led to the invention of computer. The computer was developed to produce accurate results at a very fast speed. The computer has gone through several phases of technological development. We can understand these developments by just looking at the history of computers. Before the invention of any type of calculating device, people carried out simple arithmetic calculations, such as addition and subtraction on their ﬁngers. This method of counting is still quite preferred in schools as it teaches the children about how to count. In ancient times, people also started using stones for representing numbers and carrying out simple calculations. These stones were then kept at a place suitable for adding and subtracting more stones. In that way, people performed simple arithmetic calculations. However, the use of stones did not constitute the only method of performing calculation at that time. People also used other devices—such as notches in a stick, knots in a rope, etc.—for carrying out simple calculations. However, the purpose of each device was to represent numbers. Some of the early computing devices were manually operated, while the later computing devices were completely automated. 1.2.1 Manual Computing Devices The idea of using stones for representing numbers and putting them at a place for performing simple calculations invented the device called sand table. A sand table was a device that arranged stones in three channels in the sand. Each channel could have a maximum of 10 stones. The addition operation was performed on this device by incrementing the count of right hand channel by one and by adding one stone in it. As soon as the right hand channel reached its maximum capacity, the stones were removed from that channel and one stone was added to the left hand channel. Figure 1.2 shows the idea of sand table used for the purpose of calculations. Fig. 1.2 A sand table 4 Fundamentals of Computers The idea of sand table led to the development of a fast calculating device of that time, which was known as abacus. Unlike the sand table, abacus replaced the sand frame with a wooden frame, the grooves with wires and the stones with beads. An abacus was also known as a counting frame and became popular among the people in Asia Minor around 5000 years back. This device is still in use in many parts of the world. Fig. 1.3 An abacus In this device, the wooden frame consists of many wires, with beads sliding on them. The user of an abacus can perform arithmetic operations by sliding the beads on the wires by hand. Figure 1.3 shows an abacus consisting of beads on different wires of a wooden frame. Another complicated manual comput- ing device called napier bones was developed by John Napier in the year 1614. This device was specially designed for the multiplication and quotient of numbers. Napier bones consisted of a board whose left edge was divided into 9 squares. These 9 squares were used to hold the numbers from 1 to 9. It also consisted of 10 rods, which were made up of the strips of ivory bones. The multiplication of two numbers with Napier bones could be performed in a faster manner, if one of the numbers involved in multiplication was of a single digit only. Figure 1.4 shows the arrangement of bones for the multiplication of two numbers; one is of four digits and the other of one digit. Figure 1.4 shows the process of multiplying the number 5437 with any Fig. 1.4 The napier bones Understanding the Computer 5 other number of single digit. For instance, suppose we want to multiply 5437 with 6. The computation process with this device starts with the rightmost bone and proceeds towards the left bones. The last digit in the 6th row of the 7-bone is 2, so the rightmost digit of the multiplication output is 2. After this, add the two adjacent numbers in the same row forming the parallelogram, which are 8 and 4. The addition of these two numbers is 12, so the next rightmost digit of the multiplication output is 2. Now, we have obtained 22 with a carry 1. Similarly, add the next two adjacent numbers and the carry to obtain the digit 6. At this stage, we have obtained 622 with no carry. We can proceed like this to obtain the ﬁnal answer as 32622. The idea of using bones to carry out the multiplication of numbers was modiﬁed by Edmund Gunter in 1620 to produce a device known as slide rule. This device consisted of two sets of graduated scales, which could slide over each other. The slide rule was developed not only for performing multiplication and division of numbers, but also for various scientiﬁc functions, such as logarithms, trigonometry, roots, etc. Apart from these manual computing devices, many other devices were also developed for computation purposes. Some of these devices were pascaline, stepped reckoner, punch card system etc. Pascaline was a calculator developed by Blaise Pascal in 1642. It was also known as a numerical wheel calculator. This device contained a set of toothed wheels that could be operated by hand. Pascaline was designed to handle numbers up to 999,999.999. Pascaline was further improved by German mathematician Gottfried Wilhem Von Leibriz to produce a device, called stepped reckoner. Stepped reckoner was able to perform the multiplication and division of numbers as well as calculation of the square root of a number. 1.2.2 Automated Computing Devices Charles Babbage, a professor of mathematics at the Cambridge University, made some worthwhile efforts towards automatic computing. He is also considered to be the father of modern computer. In 1812, Charles Babbage decided to automate the repeated series of steps needed in tabulating various functions, such as polynomial, logarithmic and trigonometric. In 1822, he presented a working model of his concept with the help of an automatic mechanical computing machine. He named the automatic mechanical computing machine as difference engine. In 1823, Babbage made it more automatic by providing the feature of printing the tabulated results. Babbage did not stop here and started working on developing the analytical engine. The analytical engine was considered as the completely automatic general-purpose programmable digital computer. The analytical engine was the ﬁrst device that used all the features of a modern digital computer, which include an input unit, an output unit, a storage unit, a processor and a control unit. This engine was designed to perform various mathematical operations by getting two sets of inputs from the user. The ﬁrst set of input is a program that contains a set of instructions to operate on the data. The other set of input contains the list of variables used in the program or data. The analytical engine built by Babbage in 1833 was digital, programmable and automatic. However, it was a slow engine that took almost 3 minutes to multiply two numbers of twenty ﬁgures each. In 1937, an American mathematician, Howard Aiken designed MARK I and completed it in the year 1944. MARK I was one of the well-known early computers that could perform the multiplication of two numbers of twenty ﬁgures in just 6 seconds. Hence, as compared to the analytical engine, MARK I performed calculations at a much faster speed. However, this computer was also not considered very fast from the user’s point of view because it printed the results of calculations at the rate of one result per 5 seconds. Also, MARK I computer was noisy and large in size. In the year 1944, a British mathematician, Alan Mathison developed the ﬁrst pure electronic digital programmable computer. This computer was known as Colossus. Colossus was a special purpose electronic device that used the vacuum tube technology in performing different operations. It was designed to perform only some speciﬁc functions. 6 Fundamentals of Computers The Electronic Numerical Integrator And Calculator (ENIAC) was another general-purpose electronic digital computer developed at the Moore School of Engineering of the University of Pennsylvania by John Ecker, John Mauchly and their team in the year 1946. This computer also used the vacuum tube technology in constructing the basic circuits. It was a general purpose computer that was capable of solving all types of computing problems. It included all the features and components of a modern digital computer. The internal hardware structure of ENIAC included 17,468 vacuum tubes, 1,500 relays, 70,000 registers, 7,200 crystal diodes and 10,000 capacitors. It was a bulky computer and operated at 1000 times more speed than that of MARK I computer. ENIAC was designed to perform simple arithmetic operations as well as some advanced operations, such as separating the sign of a number and comparing different numbers to check whether they are equal or not. The computer used the decimal number system for representing and processing values. In 1949, another electronic computer that used the binary number system for representing and processing values was introduced. This computer was known as Electronic Discrete Variable Automatic Computer (EDVAC). EDVAC was also invented by John Eckert and John Mauchly and was considered as the successor of ENIAC. EDVAC was the ﬁrst computer that worked on the principle of stored program. The stored program computer considers the programs and data stored in the memory as the string of binary numbers. Therefore, programs and data stored in the memory are indistinguishable inputs for the computer. The different hardware components of EDVAC were magnetic tape, control unit, dispatcher unit, processor, timer, dual memory and three temporary tanks to hold a single word. Electronic Delay Storage Automatic Calculator (EDSAC) was another early British electronic computer developed by Maurice Wilkes and his team at the University of Cambridge Mathematical Laboratory in 1949. It also used the vacuum tube technology in constructing the basic logic circuits and mercury delay lines for constructing the memory of a computer. The typical input and output unit of this computer system was punch card and teleprinter respectively. These computer systems were only able to carry out 650 instructions per second. Therefore, these computers were not considered as fast computing devices. During 1950s, Eckert-Mauchly Computer Corporation, a company of John Eckert and John Mauchly, made some serious efforts in the ﬁeld of automated computing. In 1951, the company invented the ﬁrst commercial computer that was known as Universal Automatic Computer (UNIVAC). This computer was a bulky computer that used 5200 vacuum tubes for constructing the basic logic circuits. The mercury data lines were used to construct the memory for storing data and programs. UNIVAC was able to process numbers as well as alphabetic characters in an efﬁcient manner. The important feature of UNIVAC—that made it unique among other well-known early computers—was that it provided separate processes for handling input/output and processing functions. 1.3 GENERATIONS OF COMPUTERS Over the years, various computing devices were invented that enabled the people to solve different types of problems. All these computing devices can be classiﬁed into several generations. These generations refer to the phases of improvement made to different computing devices. The different phases of improvement made to computing devices resulted in a small, cheap, fast, reliable and productive computer. The technological development in the ﬁeld of computers not only refers to the improvements made to the hardware technologies, but also the improvements made to the software technologies. The history of computer development is often discussed in terms of different generation of computers, as listed below. ∑ First generation computers ∑ Second generation computers Understanding the Computer 7 ∑ Third generation computers ∑ Fourth generation computers ∑ Fifth generation computers 1.3.1 First Generation Computers The ﬁrst generation computers were employed during the period 1940–1956. These computers used the vacuum tubes technology for calculation as well as for storage and control purposes. Therefore, these computers were also known as vacuum tubes or thermionic valves based machines. Figure 1.5 shows the vacuum tube used in ﬁrst generation computers. A vacuum tube is made up of glass and contains ﬁlaments inside it. The ﬁlaments when heated generate electrons, which eventually help in the ampliﬁcation and deampliﬁcation of electronic signals. The input and output medium for ﬁrst generation computers was the punched card and printout respectively. Some examples of ﬁrst generation computers are ENIAC, EDVAC, EDSAC and UNIVAC. The following are the two major advantages of ﬁrst generation computer systems: ∑ These computers were the fastest computing devices of their time. ∑ These computers were able to execute complex mathematical problems in an efﬁcient manner. The above two advantages of ﬁrst generation computers were not sufﬁcient enough to make these computers popular among its users. The ﬁrst generation computers had many Fig. 1.5 A vacuum tube disadvantages associated with them. The following are some of the disadvantages of ﬁrst generation computers: ∑ The functioning of these computers depended on the machine language. A machine language is a language in which all the values are represented in the form of 0s and 1s. Therefore, these computers were not very easy to program. ∑ They were generally designed as special-purpose computers. Therefore, they were not very ﬂexible in running different types of applications. ∑ The use of vacuum tube technology made these computers very large and bulky. Due to their large size, it was not an easy task to install them properly. ∑ They were not easily transferable from one place to another due to their huge size and also required to be placed in cool places. 8 Fundamentals of Computers ∑ They were single tasking because they could execute only one program at a time and hence, were not very productive. ∑ They generated huge amount of heat and hence were prone to hardware faults. Hence, they were not considered as reliable and required proper maintenance at regular intervals. 1.3.2 Second Generation Computers The second generation computers were employed during the period 1956–1963. The main characteristic of these computers was the use of transistors in place of vacuum tubes in building the basic logic circuits. The transistor was invented by Shockley, Brattain and Bardeen in 1947 for which they won the Nobel Prize. A transistor is a semiconductor device that is used to increase the power of the incoming signals by preserving the shape of the original signal. It has three connections, which are emitter (E), base (B) and collector (C). The base of transistor is the gate through which the signal, needed to be ampliﬁed, is sent. The signal sent through the base of the transistor is generally a small ﬂow of electrons. Therefore, the base terminal also acts as the input gate for the transistor. The collector of the transistor is used to collect the ampliﬁed signal. The emitter of the transistor acts as the output gate for emitting the ampliﬁed signal to the external environment. Figure 1.6 shows the transistor used to manufacture circuitry of second generation computers. The use of transistor technology helped in improving the performance of computers to a large extent. Transistor was a superior technology over vacuum tubes. Transistors used in second generation computers were smaller, faster, cheaper and generated less heat than that of vacuum tubes used in ﬁrst generation computers. Transistors were also light weight electronic devices that required very less power during their operation. These characteristic features of transistors made the second generation computers smaller, faster, cheaper, more efﬁcient, more productive and more reliable, as compared to the ﬁrst generation computers. Printers, secondary storage and operating system technology were also invented during this era. However, these computers still relied on punched card and printout for carrying out their input/output operations. Another major technological development made to these computers was the replacement of the machine language with the assembly language. Assembly language is a low-level language that allows the programmer to use simple English Fig. 1.6 A transistor words—called mnemonics—to represent different instructions in a program. Some examples of second generation computers are PDP-8, IBM 1401 and IBM 7090. The following are the advantages of second generation computers: ∑ They were the fastest computing devices of their time. ∑ They were easy to program because of the use of assembly language. ∑ They could be transferred from one place to other very easily because they were small and light weight computing devices. ∑ They required very less power in carrying out their operations. ∑ They were more reliable as compared to ﬁrst generation computers and hence, did not require maintenance at regular intervals of time. The following are the limitations of ﬁrst generation computers: ∑ The input and output media for these computers were not improved to a considerable extent. ∑ They were required to be placed in air-conditioned places. Understanding the Computer 9 ∑ The cost of these computers was very high and they were beyond the reach of home users. ∑ They were special-purpose computers and could execute only speciﬁc applications. 1.3.3 Third Generation Computers The third generation computers were employed during the period 1964–1975. The major characteristic feature of third generation computer systems was the use of Integrated Circuits (ICs). The IC technology was also known as microelectronics technology. ICs are the circuits that combine various electronic components, such as transistors, resistors, capacitors, etc. onto a single small silicon chip. The ﬁrst IC was developed by Jack Kilby and Robert Noyce in the year 1958. Figure 1.7 shows a typical IC chip used for manufacturing third generation computers. ICs were superior to vacuum tubes and transistors in terms of cost and performance. The cost of ICs was very low and the performance was very high because all the electronic components were arranged very close to each other. They also required very low power for performing their operations. Therefore, the use of ICs in third generation computers made them smaller, faster, more efﬁcient and more reliable than the ﬁrst and second generation of computers. Some examples of third generation computers are NCR 395, B6500, IBM 370, PDP 11 and CDC 7600. The following are the merits of the third generation computers: ∑ They were the fastest computing devices as compared with ﬁrst and second generation of Fig. 1.7 An integrated circuit computers. The computational time for these computers was also reduced to great extent. The computational time for these computers was usually measured in nanoseconds. ∑ They were very productive because of their small computational time. ∑ They were easily transportable from one place to another because of their small size. ∑ They used high-level languages. A high-level language is a computer programming language that is independent of the machine details. Hence, the programmer ﬁnds it very easy to use them and the programs written in these languages on one computer can be easily executed on some other computer. ∑ They could be installed very easily and required less space for their installation. ∑ They were able to execute any type of application, such as business and scientiﬁc applications. Hence, the third generation computers were also considered as general-purpose computers. ∑ They were more reliable and required less frequent maintenance schedules. Some of the disadvantages of third generation computers are: ∑ The storage capacity of these computers was still very small. ∑ The performance of these computers degraded while executing large applications, involving complex computations because of the small storage capacity. ∑ The cost of these computers was very high. ∑ They were still required to be placed in air-conditioned places. 10 Fundamentals of Computers 1.3.4 Fourth Generation Computers The fourth generation computers were employed during 1975–1989. The invention of Large Scale Integration (LSI) technology and Very Large Scale Integration (VLSI) technology led to the development of fourth generation computers. However, these computers still used the IC technology to build the basic circuits. The LSI technology allowed thousands of transistors to be ﬁtted onto one small silicon chip. On the other hand, the VLSI technology allowed hundreds of thousands of transistors to be ﬁtted onto a single chip. As a result, the manufacturers were able to reduce the size of the computers and made them cheaper as compared to the other generation of computers. The progress in LSI and VLSI technologies led to the development of microprocessor, which became the major characteristic feature of the fourth generation computers. A microprocessor incorporates various components of a computer—such as CPU, memory and Input/Output (I/O) controls—onto a single chip. The computers in this generation were designed to have a microprocessor, some additional storage chips and support circuitry. Figure 1.8 shows the Intel P4004 microprocessor chip developed in 1971. Some popular later microprocessors include Intel 386, Intel 486 and Pentium. The term Personal Computer (PC) became known to the people during this era. The term PC refers to a computer that is designed to be used by an individual. Since the size and cost of the computer was decreased to a considerable extent in this period, people started using these computers for their personal work too. The storage technologies used in the fourth generation computers were also improved and they started using static and dynamic Random Access Memory (RAM). The advantage of using this type of memory was that it allowed the computers to access the stored information at a rapid pace and hence helped in increasing the productivity and performance of the computers. Some of the examples of fourth generation computers are IBM PC, IBM PC/AT, Apple and CRAY-1. Fig. 1.8 The Intel P4004 microprocessor chip The use of LSI and VLSI technologies made the fourth generation computers small, cheap, compact and powerful. Apart from these technologies, the fourth generation also include the following developments: ∑ Development of Graphical User Interfaces (GUIs) ∑ Development of new operating systems ∑ Invention of various secondary storage and I/O devices ∑ Development of Local Area Network (LAN) Some of the advantages of fourth generation computers are as follows: ∑ The use of LSI, VLSI and semiconductor technologies made these computers very powerful in terms of their processing speed and access time. ∑ The storage capacity of these computers was very large and faster and hence they were very productive and highly optimised. ∑ They were highly reliable and required very less maintenance. ∑ They provided a user-friendly environment while working because of the development of GUIs and interactive I/O devices. Understanding the Computer 11 ∑ The programs written on these computers were highly portable because of the use of high-level languages. ∑ They were very versatile and suitable for every type of applications. ∑ They required very less power to operate. Some of the problems associated with fourth generation computers are as follows: ∑ The soldering of LSI and VLSI chips on the wiring board was not an easy task and required complicated technologies to bind these chips on the wiring board. ∑ The working of these computers is still dependent on the instructions given by the programmer. 1.3.5 Fifth Generation Computers The different types of modern digital computers come under the categories of ﬁfth generation computers. The ﬁfth generation computers are based on the Ultra Large Scale Integration (ULSI) technology that allows almost ten million electronic components to be fabricated on one small chip. The ULSI technology helps in increasing the power and speed of the microprocessor chips and the capacity of primary and secondary storage devices to a great extent. As a result, the ﬁfth generation computers are faster, cheaper and more efﬁcient, as compared to the fourth generation computers. Some of the improvements or developments made during this generation of computers are as follows: ∑ Development of various portable computers such as laptop, pocket computer, Personal Digital Assistant (PDA), etc. ∑ Development of Parallel Processors. ∑ Development of centralised computers called servers. ∑ Invention of optical disk technology. ∑ Invention of the Internet and its different services. Some of the advantages of ﬁfth generation computers are as follows: ∑ They are the fastest and powerful computers till date. ∑ They are able to execute a large number of applications at the same time and that too at a very high speed. ∑ The use of ULSI technology helps in decreasing the size of these computers to a large extent. Some of the ﬁfth generation computers are so small in size that they can be used while traveling. ∑ The users of these computers ﬁnd it very comfortable to use them because of the several additional multimedia features. ∑ They are versatile for communications and resource sharing. The ﬁfth generation computers are really enjoyed by their users because of the several advantages offered by them. However, the major disadvantage of the ﬁfth generation computers is that they are not provided with an intelligent program that could guide them in performing different operations. Nowadays, scientists are making some serious efforts in this ﬁeld and artiﬁcial intelligence and expert system applications are the results of these efforts. Figure 1.9 shows a tree of computer family that illustrates the area-wise developments during the last four decades and their contributions to the various generations of computers. 1.4 CLASSIFICATION OF COMPUTERS There are different types of computers available these days. The function of each type of computer is to process the data and provide some output to the users. However, the methods or techniques used by these 12 Fundamentals of Computers Fig. 1.9 Tree of computer family Understanding the Computer 13 computers to process and handle the data may be different. We can classify the computers according to the following three criteria: 1. Based on operating principles 2. Based on applications 3. Based on size and capability 1.4.1 Based on Operating Principles On the basis of operations performed and methods used to store and process the data and information, computers can be classiﬁed into the following categories: ∑ Analog computers ∑ Digital computers ∑ Hybrid computers Analog computers The analog computers represent data in the form of continuous electrical signals having a speciﬁc magnitude. These computers are very fast in their operation and allow several other operations to be carried out at the same time. However, the results produced by these computers are not very accurate. Therefore, the analog computers are widely used in applications in which the accuracy of results is not a major concern. They are powerful tools to solve differential equations. The electronic circuit employed in modern analog computers is generally an Operational Ampliﬁer (Op-Amp). It is made up of semiconductor integrated circuits. The three different characteristic features of Op-Amps are as follows: ∑ They have large voltage gain. The voltage gain of an ampliﬁer is deﬁned as the ratio of the output voltage to the input voltage. ∑ They have inﬁnite input resistance. The input resistance is deﬁned as the ratio of change in the input voltage to the change in input current. ∑ They have zero output resistance. The output resistance is the nominal resistance measured with no load. Figure 1.10 shows the basic circuit used in analog computers. In Fig. 1.10, the triangle represents an ampliﬁer that is used to invert the incoming signal. If the incoming signal is a positive signal, then it will be inverted into a negative output signal. Similarly, if the incoming signal is a negative signal, then it will be inverted into a positive output signal. Rf and Rin are used to represent the feedback resistor and the input resistor respectively. Fig. 1.10 Integrated circuit of an operational ampliﬁer Digital computers The digital computer, also known as the digital information processing system, is a type of computer that stores and processes data in the digital form. Therefore, each type of data is usually stored in these computers in terms of 0s and 1s. The output produced by these computers is also in the digital form. The digital computers are also capable of processing the analog data. However, the analog data should be ﬁrst converted to the digital form, before being processed by these computers. Similarly, if we want the output in the analog form, then the digital information produced by these computers should be ﬁrst converted to an analog form. These conversions are generally carried out by the in-built components of digital computers. 14 Fundamentals of Computers Digital computers are generally faster and more reliable than the analog computer systems and provide more accurate results. The computer used by a home user is a typical example of digital computer. The digital computers are also employed in colleges, universities and small and medium sized businesses. The different hardware components of a digital computer are an Arithmetic-Logic Unit (ALU), a Control Unit (CU), a memory unit and I/O units. The ALU of a digital computer is used to perform various arithmetic operations, such as addition, subtraction, multiplication and division and various logic operations such as AND, OR, NOT, etc. CU helps in directing the operations of ALU. The memory unit is used to store the data on temporary or permanent basis. The input units are used to enter the data into the computer and the output units is used to display the information generated by the computer to the user. Hybrid computers The hybrid computer is a combination of analog computer and digital computer because it encompasses the best features of both these computers. Therefore, the hardware components of hybrid computers are usually the mixture of analog and digital components. These features make the hybrid computers very fast, efﬁcient and reliable. In these computers, data is generally measured and processed in the form of electrical signals and is stored with the help of digital components. However, these computers can also be used to perform various types of logical operations. The input accepted by the hybrid computers is a continuously varying input signal. This input signal is then converted by them into a set of discrete values for performing different operations. These computers prove to be very cost-effective in performing complex simulations. The hybrid computers are also less expensive than the digital computers. The computer used in hospitals to measure the heartbeat of the patient is a very good example of a hybrid computer. Apart from this, the hybrid computers are also used in scientiﬁc applications, various engineering ﬁelds and in controlling business processes. 1.4.2 Based on Applications Different computers are designed for different purposes so that they can perform their tasks according to their capabilities. On the basis of different applications or purposes, computers can be classiﬁed into the following categories: ∑ General purpose computers ∑ Special purpose computers General purpose computers They are designed in such a manner that they can work in all environments. The general purpose computers are versatile and can store a number of programs meant for performing distinct tasks. However, the general purpose computers are not efﬁcient and consume a large amount of time in generating the result. Special purpose computers They are designed in such a manner that they can perform only a speciﬁed task. The special purpose computers are not versatile and their speed and memory size depend on the task that is to be performed. These computers are less expensive as they do not contain any redundant information. The special purpose computers are efﬁcient and consume less amount of time in generating the result. 1.4.3 Based on Size and Capability Computers differ from each other in terms of their shape, size and weights. Each type of computer performs some unique functions and can be employed in the ﬁelds suited for them. These computers also differ in terms of processing speed. Some of them are of moderate speed, whereas some others operate at a very fast speed. On the basis of size and capability, computers can be classiﬁed into the following categories: Understanding the Computer 15 ∑ Microcomputers ∑ Mini computers ∑ Mainframe computers ∑ Super computers Microcomputers A microcomputer is a small and cheap digital computer that is designed to be used by individuals. It is built around a microprocessor, a storage unit and an I/O channel. Apart from these components, the other parts that a microcomputer includes are power supply, connecting cables, keyboard, mouse, printer and scanner. These computers also include several software programs such as operating system, system software and utility software. The micro computers are generally available in the form of PCs, workstations and notebook computers. Figure 1.11 shows the block diagram of a microcomputer. Fig. 1.11 The block diagram of a microcomputer Microprocessor It is the heart of the microcomputer. It incorporates all the functions of a CPU onto a single IC in a microcomputer. The basic units of microprocessor are ALU, register unit and CU. ALU is used to perform various arithmetic and logic operations. The register unit is used to store the data and instructions temporarily needed by the ALU. The various registers used by a microcomputer are Accumulator (AC), program control register, I/O register, instruction register, Memory Address Register (MAR) and Memory Buffer Register (MBR). CU is used to manage and direct the operations performed by the microcomputer. Memory It is used to store the data and instructions on temporary or permanent basis. A microcomputer generally employs two types of memories, i.e., primary memory and secondary memory. Primary memory, also called main memory, is used to store the data and instructions temporarily. It stores only those instructions and data that are needed by the microprocessor of the computer for processing. The secondary memory, also called auxiliary memory, is used to store the data and instructions permanently. Magnetic disks and magnetic tapes are some of the examples of secondary storage. Peripheral devices They are generally the input and output devices attached to the computer. The various input devices—such as keyboard and mouse—are used to enter program and data into the computer 16 Fundamentals of Computers before performing any kind of operation. They are used to transfer data and instructions from the external environment into the computer. The various output devices—such as monitor and printer—are used to display the results computed by the computer to the user. The major function performed by the output devices is to convert the binary result computed by the computer into a form that can be easily understood by the users. System bus It is also referred to as the frontside bus, memory bus, local bus or host bus. The system bus in the micro computer is used to connect microprocessor, memory and peripheral devices into a single unit. The system bus is a collective name given to address, data and control bus. The address bus is a unidirectional bus that is used to identify a peripheral device or a memory location. The data bus is a bidirectional bus that is used to transfer data among microprocessor, memory and peripheral devices of the computer. The control bus is used by the microprocessor to send control signals to the various devices within the computer. Depending on the size, the microcomputer can be further classiﬁed into the following types: Desktop computer It is also known as PC. The desktop computer systems are designed to be used by an individual at a single location. The typical components of a desktop computer are keyboard, mouse, monitor, hard disk storage, peripheral devices and a system unit. These computers are very cheap and an individual can easily purchase them for home or business use. The different manufacturers of desktop computers are Apple, IBM, Dell and Hewlett-Packard (HP). Laptop computer It is a portable computer that can be taken from one place to another at any time very easily. It is also known as notebook computer, notepad or mobile computer. The laptop computer is a small size computer that incorporates all the features of a typical desktop computer. These computers are provided with a rechargeable battery that removes the need of continuous external power supply. However, these computer systems are more expensive than desktop computers. The different manufacturers of laptop computers are Acer, Apple, Panasonic, Sony and HP. Hand-held computer It is also known as Personal Digital Assistant (PDA), converged device, palmtop or mobile device. The hand-held computer is a very small size computer that can be kept in pocket. It generally has a very small display screen and the input device for these computers is a pen or an electronic stylus. The storage capacity of hand-held computers is not very large. They generally use small cards to store data and programs instead of disk drives. Therefore, they are less powerful as compared to the desktop and laptop computers. The different examples of hand-held computers are Apple Newton, Casio Cassiopeia, Franklin eBookMan, etc. Mini computers A mini computer was ﬁrst introduced in the year 1960 by Digital Equipment Corporation (DEC). They were called mini computers because of their smaller size than the other computers of those times. They can handle more data and more input and output than micro computers. Mini computers are less powerful than mainframe computers but more powerful than micro computers. Therefore, they are also referred to as the midrange computers. They are able to cater to the needs of multiple users at a single instant of time. The number of users supported by mini computers may range between 4 and 200. These computers are generally designed for small and medium sized business environments. Mini computers are generally used in business environments as the centralized computer or the network server. After implementing the mini computer as the network server, hundreds of desktop computers can be connected to it. Mini computers can also be used as the web servers that can handle thousands of transactions in a day. These computers are less expensive than mainframe computers and hence suitable for Understanding the Computer 17 those organizations that cannot afford high priced servers. The different examples of mini computers are PDP 11, IBM (8000 series), VAX 7500, etc. Mainframe computers A mainframe computer is a very large computer that is employed by large business organisations for handling major applications, such as ﬁnancial transaction processing, Enterprise Resource Planning (ERP), industry and consumer statistics, and census. They are capable of handling almost millions of records in a day. The mainframe computers can also be used as the centralised computers with several user terminals connected to it. The mainframe computers are actually considered as the predecessor of servers. These computers are bigger and more expensive than other computers. The implementation of mainframe computers also requires large space with a closely monitored humidity and temperature levels. These computers are termed as mainframe because all the hardware units are arranged into a frame. The different manufacturers of mainframe computers are IBM, Amdahl, Hitachi, etc. Examples of mainframe computers are IBM 3000, VAX 8000 and CDC 6600. The mainframe computers can maintain large databases that can be accessed by remote users with a simple terminal. Therefore, the mainframe computers are also known as super servers or database servers. The processing speed of these computers is generally optimised by employing more than one microprocessor to execute millions of instructions per second. The mainframe computers also have large capacity of primary and secondary storage as compared with other types of computers. Some of the characteristic features of mainframe computers are as follows: ∑ A typical mainframe computer generally has a maximum of 16 microprocessors. However, some modern mainframe computers can have more than 16 microprocessors. ∑ The RAM capacity of these computers lies between 128 MB and 8 GB. ∑ They are able to run multiple operating systems, and therefore, termed ‘virtual machines’. ∑ They have different cabinets for primary storage, secondary storage and I/O units. ∑ They can handle huge amount of I/O operations at the same time. Super computers A super computer is the fastest type of computer that can perform complex operations at a very high speed. The super computers were ﬁrst presented in the year 1960 by Seymour Cray at Control Data Corporation (CDC). They are more expensive than the other categories of computers and are specially designed for the applications in which large number of complex calculations have to be carried out to get the desired output. The main reason behind the fast speed of super computers is that they are designed only to execute small number of programs at a time rather than many programs simultaneously. Some of the manufacturers of super computers are IBM, Silicon Graphics, Fujitsu, Intel, etc. Examples of Super Computers are CRAY 3, Cyber 205, NEC SX-3 and PARAM from India. The various application areas of super computers are as follows: ∑ Weather forecasting ∑ Animated graphics ∑ Fluid mechanics ∑ Nuclear energy research ∑ Petroleum exploration Super computers are manufactured with no special hardware. Like the typical computer, they have CPU and memory as their major components. However, the CPU of super computer operates at faster speed, as compared to the other categories of computers. Super computers are the fastest computers because they employ thousands of processors, hundreds of gigabytes of RAM and thousands of gigabytes of secondary storage. 18 Fundamentals of Computers The designers of super computers use two different methods for optimising their performance. These methods are pipelining and parallelism. Pipelining is a technique that allows the microprocessors to execute the second instruction before the execution of the ﬁrst instruction is completed, whereas parallelism allows the microprocessors to execute several instructions at the same time. In this type of computing, a large and complex problem is ﬁrst divided into smaller problems, that are solved concurrently by the microprocessor of the computer. 1.5 COMPUTING CONCEPTS We can understand how a computer functions by analysing the fundamental computing concepts. The most elementary computing concepts include receiving input—known as data— from the user, manipulating the input according to the given set of instructions and delivering the output—known as information—to the user. Figure 1.12 shows the functioning of a computer based on these concepts. The various functions performed Fig. 1.12 The Input-Process-Output Cycle of a computer by the computer are brieﬂy described below: Accepting the raw data The ﬁrst task to be performed by a computer is to accept the data from the user, with the help of an input device, such as mouse and keyboard. Mouse is used to enter the data through point-and-click operation while keyboard is used to enter the character data by typing the various keys. We need to enter the data into the computer so as to obtain the required result as output. Processing the data The data is processed with the help of speciﬁc instructions known as programs after taking the input from the user. The manipulation of data is handled by the CPU of the computer. CPU is considered as the brain of the computer because it controls the execution of various instructions. The raw data entered by the user through input devices is processed by the CPU to generate meaningful information. Storing the data The data is stored in the main memory of a computer in its processed form. The various external storage devices—such as hard disk and magnetic disk—can also be used for storing the processed data so that it can again be fetched later. Delivering the output The processed data is delivered as useful information to the user with the help of output devices, such as printer and monitor. 1.6 THE COMPUTER SYSTEM A Computer System, small or big, in order to carry out its functions successfully, must essentially include the following four sub-systems: ∑ Hardware Understanding the Computer 19 ∑ Software ∑ Data ∑ People 1.6.1 Hardware The physical devices that make up the computer are called Hardware. The hardware units are responsible for entering, storing and processing the given data and then displaying the output to the users. The basic hardware units of a general purpose computer are keyboard, mouse, memory, CPU, monitor and printer. Among these hardware units, keyboard and mouse are used to input data into the computer, memory is used to store the entered data, CPU is used to process the entered data and monitor and printer are used to display the processed data to the users. CPU is the main component inside the computer that is responsible for performing various operations and also for managing the input and output devices. It includes two components for its functioning, Arithmetic Logic Unit (ALU) and Control Unit (CU). ALU is used to perform the arithmetic operations, such as addition, subtraction, etc. and logic operations, such as AND, OR, etc. on the data obtained from the memory. CU is used to control the activities related to the input and output devices. It obtains the instructions from the memory, decodes them and then, executes them, so as to deliver output to the users. 1.6.2 Software The term software refers to a set of programs and instructions that help the computers in carrying out their processing. Software is very necessary for the proper functioning of a computer. There are mainly two types of software, viz. Application Software and System Software: Application software The programs, which are designed to perform a speciﬁc task for the user, are known as application software. Application software is also referred as end-user programs because its functions are used by the user for obtaining the desired results. Word processor, database programs, presentation programs and spreadsheets are the examples of application software. System software The programs, which are designed to control the different operations of the computer, are known as system software. It mainly manages the activities of the computer hardware and interacts with the application software to perform a particular task. Operating systems, compilers, assemblers, interpreters and device drivers are the examples of system software. 1.6.3 Data Data refer to the raw facts and pieces of information that is usually entered into the computer system by the user, so as to generate the desired output. The data are presented in the form understandable by the computer system and the result is delivered in the form understandable by the users. In a computer system, data are manipulated by the program consisting of different instructions. Depending on the requirement, data can be presented in two forms, viz. Quantitative and Qualititative. Qualitative data The data, which are represented in words or text form, are known as qualitative data. This type of data can also include images, videos and audios used for the graphical presentation. Quantitative data The data, which are represented in numerical form, are known as quantitative data. This type of data include different numbers and symbols used for representing a particular quantity. The data entered by a user into the computer system can be in the form of numbers, text or images. The data—stored in the memory of the computer system—is in the form of bits and bytes. A bit is deﬁned as the smallest unit of information used in the computer system and a byte equals to a group of eight bits. 20 Fundamentals of Computers 1.6.4 People Computer systems are designed by the people, for the people. People, therefore, include the people who design and build hardware and software (known as systems people) and the people who actually use computer systems for their applications (known as users). Systems people include hardware engineers, software engineers, programmers, etc. Users might include a variety of people working in different areas of applications, such as education, business, entertainment, training, etc. Users may use the available standard software or develop their own software depending upon their requirements. 1.7 APPLICATIONS OF COMPUTERS Today, computers are used in almost every sphere of life. The users from different locations can easily and quickly communicate with each other with the help of computers. The use of computers has reduced the paper work to a large extent. Thus, computers have become a basic need to perform various tasks in our day-to-day life. Some common applications of computers are discussed below. Education Computers are used in schools and colleges to teach students in a better and easy way. The students can get more information about a speciﬁc topic or subject using the Internet. Computers help in easy learning by creating presentations on a speciﬁc topic. Today, students can ﬁll their application forms and give their exams online that facilitates distance education. Computer-based learning and web-based learning are very popular amongst students. Business Computers are used in different types of business to store a large amount of information in the form of databases. Using computers, business meetings can be held between people sitting at remote locations through web conferencing. Buyers and sellers can conduct business online through the use of computers and Internet. Communication Computers that are connected with each other can be used to transfer data to and from other computers. In order to establish communication between two users, Internet is one of the most common mediums. E-mail is a popular system through which a user can send/receive text messages, graphic messages and ﬁle attachments. Science Computers are used by various scientists for the purpose of research and development. They generally make use of computer for research and analysis of new theories. With the help of computers, scientists are moving towards the possibility of predicting natural disasters, such as earthquake and tsunami. Engineering Computers are used by the engineers for the creation of complex drawings and designs while working in different ﬁelds, like automobiles and construction. Engineers use computers extensively for numerical computing. Entertainment Computers are used in the entertainment industry for creating graphics and animations. There are various free as well as proprietary graphics softwares available for creating graphics and animations. Banking Nowadays, computers are being increasingly used for online banking. Through online banking, the users or customers can transfer and receive money by using computers and Internet. Some banks also provide the facility of online bill payment through their websites. Understanding the Computer 21 Health Computers are used by doctors to diagnose various kinds of diseases and ailments. Several analog and digital devices are connected with computers enabling the doctors to monitor the condition of a patient and view the internal organs of the body. Hospitals use computers to maintain and manage patient records and billing systems. They also use the concept of ‘tele-medicine’ to serve the patients at remote locations. Government Computers play a crucial role in almost all government departments. Revenue, industry, census, police, defense and many other departments use computers extensively to serve the people better. The concept of ‘e-governance’ is becoming popular among various government agencies. Chapter Summary Computer is a machine that accepts the data as input and stores and processes them, based on the instructions provided by the user. A computer basically consists of hardware and software. Along with these components, the data and users are also related to a computer as without them a computer cannot function. Hardware refers to the physical components of the computer, such as keyboard, mouse, CPU and printer. Software refers to the set of instructions provided to the computer by the user for performing a speciﬁc task. Data refers to the type of input given by the user to the computer; it can be in the form of numbers, words or images. Users refer to the persons who use the computer for getting the required result corresponding to the given input. Computers are used for performing complex calculations at a very fast speed. Earlier, the manual computing devices, such as sand table, abacus and napier bones were used for performing different calculations. These devices consumed a large amount of time and were unable to handle large numbers in calculations. Due to the drawbacks of manual computing devices, the automated computing devices such as MARK I, ENIAC and EDVAC were developed for performing calculations automatically. These devices are much faster as compared to the manual computing devices. There are ﬁve generations of computers associated with the development of computers. During these generations, the computers have seen tremendous shift in technology, size, and speed. Computers can be classiﬁed into three categories—analog computers, digital computer and hybrid computers—on the basis of their operating principles. Depending upon their application areas, computers are categorised into two types, general purpose computers and special purpose computers. On the basis of the size and capability, computers are categorised into four types, micro computers, mini computers, super computers and mainframe computers. These days, computers are being used in almost every ﬁeld because of their high processing speed and large storage capacity. Education, science, business and healthcare are some of the areas where computers are widely used. Key Terms to Remember ∑ Computer: An electronic machine that takes input from the user and stores and processes it to generate the output in the form of useful information to the user. ∑ Data: The raw details that need to be processed to generate some useful information. ∑ Program: The set of instructions that can be executed by the computer in sequential or non-sequential manner. ∑ Information: Processed data useful for the user. ∑ CPU: The processor of the computer that is responsible for controlling and executing instructions. ∑ Monitor: A screen, which displays the information in the visual form, after receiving the video signals from the computer. ∑ Transistor: A semiconductor device that is used to increase the power of the incoming signals by preserving the shape of the original signal. 22 Fundamentals of Computers ∑ Microprocessor: An integrated circuit that contains the entire central processing unit of a computer on a single chip. ∑ Vacuum Tube: An electron tube from which all or most of the gas has been removed, permitting electrons to move with low interaction with any remaining gas molecules. ∑ LSI: Large Scale Integration ∑ VLSI: Very large-scale integration (VLSI) refers to an IC or technology with many devices on one chip. ∑ ULSI: Ultra-large-scale integration ∑ ICs: The circuits that combine various electronic components, such as transistors, resistors, capacitors, etc. onto a single small silicon chip. ∑ Analog Computer: A type of computer which represents data in the form of continuous signals. ∑ Digital computer: A type of computer that stores and processes data in digital form and is also known as the digital information processing system. ∑ Hybrid computer: A combination of analog computer and digital computer because it encompasses the best features of both these computers. ∑ Microcomputer: A small digital computer that is designed to be used by individuals. ∑ Super computer: The fastest type of computer that can perform complex operations at a very high speed. ∑ Mainframe computer: A very large computer that is employed by large business organisations for handling major applications, such as ﬁnancial transaction processing applications and ERP. ∑ Hardware: A group of electronic devices that make up a computer. They are used for performing tasks, such as entering the data, processing of data and then displaying the output to the users. ∑ Software: The programs and instructions that help the computer in carrying out their processing. ∑ Application software: The programs, which are designed to perform a speciﬁc task for the user. ∑ System software: The programs, which are designed to control the different operations of the computer system. Review Questions Fill in the Blanks 1. A ___________ is an electronic machine that takes input from the user and stores and processes the given input to generate the output in the form of useful information to the user. 2. The raw details that need to be processed to generate some useful information is known as ___________. 3. The set of instructions that can be executed by the computer is known as ___________. 4. ___________ is the processor of the computer that is responsible for controlling and executing the various instructions. 5. ___________ is a screen, which displays the information in visual form, after receiving the video signals from the computer. 6. A ___________ was a device that arranged stones in three channels in the sand. 7. In ___________, the wooden frame consists of many wires with beads sliding on them and it was also known as a counting frame. 8. ___________ computing device consists of a board whose left edge is divided into 9 squares and these 9 squares are used to hold the numbers from 1 to 9. Understanding the Computer 23 9. ___________ is considered to be the father of modern digital computers. 10. The ___________ was the ﬁrst device that used all the features of a modern digital computer. 11. Colossus was a special purpose electronic device that used the ___________ technology to perform different operations. 12. ___________ computers were also known as vacuum tubes or thermionic valves based machines. 13. A ___________ is a semiconductor device that is used to increase the power of the incoming signals by preserving the shape of the original signal. 14. ___________ is a low-level language that allows the programmer to use simple English words, called mnemonics, to represent different instructions in a program. 15. The main characteristic feature of third generation computers was the use of ___________. 16. The invention of ___________ and ___________ technology led to the development of the fourth generation computers. 17. The ﬁfth generation computers are based on the ___________ technology that allows almost te

Fundamentals of Computers PDF

Document Details

Tags

Related

Summary

Full Transcript

Upgrade to continue