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Introduction to Computer System/ 1
Chapter 1
INTRODUCTION TO COMPUTER SYSTEM
**1. 0 Objectives
- 1 Introduction – Computer?
- 2 Evolution of Computers
- 3 Classification of Computers
- 4 Applications of Computers
- 5 Advantages and Disadvantages of Computers
- 6 Similarities Difference between computer and Human 1.7 A Computer System
- 8 Components of a Computer System
- 9 Summary
- 10 Check your Progress -** Answers 1. 11 Questions for Self – Study 1.12 Suggested Readings
1. 0 OBJECTIVES After studying this chapter you will be able to: Learn the concept of a system in general and the computer system in specific. Learn and understand how the computers have evolved dramatically within a very short span, from very huge machines of the past, to very compact designs of the present with tremendous advances in technology. Understand the general classifications of computers. Study computer applications. Understand the typical characteristics of computers which are speed, accuracy, efficiency, storage capacity, versatility. Understand limitations of the computer. Discuss the similarities and differences between the human and the computer. Understand the Component of the computer. 1 .1 INTRODUCTION- Computer Today, almost all of us in the world make use of computers in one way or the other. It finds applications in various fields of engineering, medicine, commercial, research and others. Not only in these sophisticated areas, but also in our daily lives, computers have become indispensable. They are present everywhere, in all the dev ices that we use daily like cars, games, washing machines, microwaves etc. and in day to day computations like banking, reservations, electronic mails, internet and many more. The word computer is derived from the word compute. Compute means to calculate. The computer was originally defined as a super fast calculator. It had the capacity to solve complex arithmetic and scientific problems at very high speed. But nowadays in addition to handling complex arithmetic computations, computers perform many other tasks like accepting, sorting, selecting, moving, comparing various types of information. They also perform arithmetic and logical operations on alphabetic, numeric and other types of information. This information provided by the user to the computer is data. The information in one form which is presented to the computer is the input information or input data.
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Information in another form is presented by the computer after performing a process on it. This information is the output information or output data. The set of instructions given to the computer to perform various operations is called as the computer program. The process of converting the input data into the required output form with the help of the computer program is called as data processing. The computers are therefore also referred to as data processors Therefore a computer can now be defined as a fast and accurate data processing system that accepts data, performs various operations on the data, has the capability to store the data and produce the results on the basis of detailed step by step instructions given to it.. The terms hardware and software are almost always used in connection with the computer.
- The Hardware: The hardware is the machinery itself. It is made up of the physical parts or devices of the computer system like the electronic Integrated Circuits (ICs), magnetic storage media and other mechanical devices like input devices, output devices etc. All these various hardware are linked together to form an effective functional unit. The various types of hardware used in the computers, has evolved from vacuum tubes of the first generation to Ultra Large Scale Integrated Circuits of the present generation. - The Software: The computer hardware itself is not capable of doing anything on its own. It has to be given explicit instructions to perform the specific task. The computer program is the one which controls the processing activities of the computer. The computer thus functions according to the instructions written in the program. Software mainly consists of these computer programs, procedures and other documentation used in the operation of a computer system. Software is a collection of programs which utilize and enhance the capability of the hardware .
Check your Progress - 1. 1
1. Fill in the blanks. a. The set of instructions to perform various operations is called a ………………… b. Compute means to …………. of the computer. c. Mechanical devices are a type of.................. 2. Answer in brief. a. Define a computer. ............................................................................................................. ............................................................................................................. b. W hat is software? ............................................................................................................. ..............................................................................................................
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Charles Babbage a British mathematician at Cambridge University invented the first analytical engine or difference engine. This machine could be programmed by instructions coded on punch cards and had mechanical memory to store the results. For his contributions in this field Charles Babbage is known as ‘the father of modern digital computer. Some of the early computers included: Mark I – This was the first fully automatic calculating machine. It was designed by Howard Aiken of Harvard University in collaboration with IBM. This machine was an electronic relay computer. Electromagnetic signals were used for the movement of mechanical parts. Mark I could perform the basic arithmetic and complex equations. Although this machine was extremely reliable, it was very slow (it took about 3 - 5 seconds per calculation) and was complex in design and large in size. Atanasoff-Berry Computer (ABC) – This computer developed by John Atanasoff and Clifford Berry was the world’s first general purpose electronic digital computer. It made use of vacuum tubes for internal logic and capacitors for storage. ENIAC (Electronic Numeric Integrator and Calculator) – The first all electronic computer was produced by a partnership between the US Government and the University of Pennsylvania. It was built using 18 , 000 vacuum tubes, 70 , 000 resistors and 1 , 50 0 relays and consumed 160 kilowatts of electrical power. The ENIAC computed at speed about thousand times faster than Mark I. However, it could store and manipulate only a limited amount of data. Program modifications and detecting errors were also difficult. Fig. 1.3 ENIAC EDVAC – In the mid 194 0’s Dr. John von Neumann designed the Electronic Discrete Variable Automatic Computer with a memory to store both program and data. This was the first machine which used the stored program concept. It had five distinct units - arithmetic, central control, memory, input and output. The key element was the central control. All the functions of the computer were co-ordinate through this single source, the central control. The programming of the computers was done in machine language UNIVAC • I – Remington Rand designed this computer specifically for business data processing applications. The Universal Automatic Computer was the first general purpose commercially available computer. Fig 1.4 UNIVAC
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1. 2. 2 The Second Generation: In the second generation computers: Vacuum tube technology was replaced by transistorized technology, Size of the computers started reducing, Assembly language started being used in place of machine language, Concept of stored program emerged, High level languages were invented. This was the generation of Transistorized Computers. Vacuum tubes were replaced by transistors. As a result, the size of the machines started shrinking. These computers were smaller, faster, more reliable and more energy efficient. The first transistorized computer was TX- 0. The first large scale machines that took advantage of the transistor technology were the early supercomputers, Stretch by IBM and LARC by Sperry Rand. These machines were mainly developed for atomic energy laboratories. Typical computers of the second generation were the IBM 1400 and 7000 series, Honeywell 200 and General Electric. Fig 1.5 Transistors IBM 1401 was universally accepted throughout the industry and most large businesses routinely processed financial information using second generation computers. The machine language was replaced by assembly language. Thus the long and difficult binary code was replaced with abbreviated programming code which was relatively easy to understand. The stored program concept and programming languages gave the computers flexi bility to finally be cost effective and productive for business use. The stored program concept implied that the instructions to run a computer for a specific task were held inside the computer’s memory and could quickly be modified or replaced by a different set of instructions for a different function. High level languages like COBOL, FORTRAN and AL- GOL were dev eloped. Computers started finding vast and varied applications. The entire software industry began with the second generation computers. 1. 2. 3. The Third Generation: The third generation computers were characterized by: Use of Integrated circuits, Phenomenal increase in computation speed, Substantial reduction in size and power consumption of the machines, Use of magnetic tapes and drums for external storage, Design-of Operating systems and new higher level languages, Commercial production of computers. This generation was characterized by the invention of Integrated Circuits (ICs). The 1 C combined electronic components onto a small chip which was made from quartz.
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Computers (PCs) commenced. In 1981 , IBM introduced its personal computer for use in office, home and schools. In direct competition, the Macintosh was introduced by Apple in 1984. Shared interactive systems and user friendly environments were the features of these computers. As the computers started becoming more and more powerful, they could be linked together or networked to share not only data but also memory space and software. The networks could reach enormous proportions with local area networks. A global web of computer circuitry, the Internet, links the computers worldwide into a single network of information. 1. 2. 5 The Fifth Generation: Defining the fifth generation computers is somewhat difficult because the field is still in its infancy. The computers of tomorrow would be characterized by Artificial Intelligence (At). An example of Al is Expert Systems. Computers could be developed which could think and reason in much the same way as humans. Computers would be able to accept spoken words as input (voice recognition). Many advances in the science of computer design and technology are coming together to enable the creation of fifth generation computers. Two such advances are parallel processing where many CPUs work as one and advance in superconductor technology which allows the flow of electricity with little or no resistance, greatly improving the speed of information flow. **Check your Progress - 1. 2
- Match the following. A B** a) Very Large scale Integration I) Second Generation b) Vacuum Tube Technology II) Fifth Generation c) Stored Program III) Fourth Generation d) Superconductor Technology IV) First Generation e) Semiconductor Technology v) Third Generation 2. Write True or False A. Expert system is an example of artificial Intelligence. B. The world’s first general purposes electronic digital computer was the Abacus. C. The first generation computers used machine language for programming. D. Charles Babbage designed the Analytical Engine. E. Personal Computer (PC) was developed in the first generations. 1. 3 CLASSIFICATION OF COMPUTERS Computers are broadly classified into two categories depending upon the logic used in their design as: 1.3.1 Analog computers: In analog computers, data is recognized as a continuous measurement of a physical property like voltage, speed, pressure etc. Readings on a dial or graphs are obtained as the output, ex. Voltage, temperature; pressure can be measured in this way.
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1.3.2 Digital Computers: These are high speed electronic devices. These devices are programmable. They process data by way of mathematical calculations, comparison, sorting etc. They accept input and produce output as discrete signals representing high (on) or low (off) voltage state of electricity. Numbers, alphabets, symbols are all represented as a series of 1 s and Os. Digital Computers are further classified as General Purpose Digital Computers and Special Purpose Digital Computers. General Purpose computers can be used for any applications like accounts, payroll, data processing etc. Special purpose computers are used for a specific job like those used in automobiles, microwaves etc. Another classification of digital computers is done on the basis of their capacity to access memory and size like:
- Small Computers: I) Microcomputers: Microcomputers are generally referred to as Personal Computers (PCs). They have Smallest memory and less power. They are widely used in day to day applications like office automation, and professional applications, ex. PC- AT, Pentium etc. II) Note Book and Laptop Computers: These are portable in nature and are battery operated. Storage devices like CDs, floppies etc. and output devices like printers can be connected to these computers. Notebook computers are smaller in physical size than lap top computers. However, both have powerful processors, support graphics, and can accept mouse driven input. Microcomputer Notebook or Laptop Handheld Computer Fig. 1.8 Small Computers III) Hand Held Computers: These types of computers are mainly used in applications like collection of field data. They are even smaller than the note book computers.
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weather forecasting, and complex mathematical and engineering applications. Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) help in designing robotics, automobile manufacturing, automatic process control dev ices etc. 1.4.2 Business: Record keeping, budgets, reports, inventory, payroll, invoicing, accounts are all the areas of business and industry where computers are used to a great extent. Database management is one of the major area where computers are used on a large scale. The areas of application here include banking, airline reservations, etc. where large amounts of data need to be updated, edited, sorted, searched from large databases. 1.4.3 Medicine: Computerized systems are now in widespread use in monitoring patient data like , pulse rate, blood pressure etc. resulting in faster and accurate diagnosis. Modern day medical equipment are highly computerized today. Computers are also widely used in medical research. 1.4.4 Information: This is the age of information. Television, Satellite communication, Internet, networks are all based on computers. 1.4.5 Education: The use of computers in education is increasing day by day. The students develop the habit of thinking more logically and are able to formulate problem solving techniques. CDs on a variety of subjects are available to impart education. On line training programs for students are also becoming popular day by day. All the major encyclopedias, dictionaries and books are now available in the digital form and therefore are easily accessible to the student of today. Creativity in drawing, painting, designing, decoration, music etc. can be well developed with computers. 1.4.6 Games and Entertainment: Computer games are popular with children and adults alike. Computers are nowadays also used in entertainment areas like movies, sports, advertising etc. Advantages of Computers: 1.5.1 Speed: The speed of a computer is measured in terms of the number of instructions that it can perform or execute in a second. The speeds of computers are measured in millise conds (10~ 3 sec), micro-seconds (10* 6 sec), and nano-seconds (10~9sec). Computers are superfast machines and can process millions of instructions per second. Smaller computers can execute thousands of instructions per second, while the more complex machines can execute millions of instructions per second. 1.5.2 Accuracy: Computers are very accurate. They are capable of executing hundreds of instructions without any errors. They do not make mistakes in their computations. They perform each and every calculation with the same accuracy. 1.5.3 Efficiency The efficiency of computers does not decrease with age. The computers 1 .5 ADVANTAGES AND DISADVANTAGES OF COMPUTERS
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can perform repeated tasks with the same efficiency any number of times without exhausting there selves. Even if they are instructed to execute millions of instructions, they are capable of executing them all with the same speed and efficiency without exhaustion. 1.5.4 Storage Capability Computers are capable of storing large amounts of data in their storage devices. These dev ices occupy very less space and can store millions of characters in condensed forms. These storage devices typically include floppy disks, tapes, hard disks, CDs etc, the data stored on these devices can be retrieved and reused whenever it is required in future 1.5.5 Versatility Computers are very versatile. They are capable not only of performing complex mathematical tasks of science and engineering, but also other non- numerical operations fielding air-line reservation, electricity bills, data base management etc. Limitations of Computers: Although the computers of today are highly intelligent and sophisticated they have their own limitations. The computer cannot think on its own, since it does not have its own brain. It can only do what is has been programmed to do. It can execute only those jobs that can be expressed as a finite set of instructions to achieve a specific goal. Each of the steps has to be clearly defined. The computers do not learn from previous experience nor can they arrive at a conclusion without going through all the intermediate steps. However the impact of computers on today’s society in phenomenal and they are today an important part of the society. Check your Progress - 1 .4 & 1. Select the appropriate option a. The number of instructions a computer can process in a given time is called its (i) Versatility (ii) Speed (iii) Efficiency (iv) Accuracy Answer the following: a) Give any one application of modern day computers ................................................................................................................................. ................................................................................................................................. b) State in brief one or two limitations of computers. ................................................................................................................................. ................................................................................................................................. Computer is a very effective and efficient machine which performs several activities in few minutes, which otherwise would have taken several days if performed naturally. Besides there would have been a doubt about the accuracy, finish etc. The computer may be faster; more accurate but it cannot compete with human brain. However there are some similarities between the human and the computer which would make the computer more understandable. 1.6 Similarities and Difference between Human and Computer
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designed to achieve a common objective. Thus, a system is made up of more than one element or part, where each element performs a specific function and where all the elements (parts) are logically related and are controlled in such a way that the goal (purpose) of the system is achieved. A computer is made up of a number of integrated elements like
- The central processing unit,
- The input and output devices and
- The storage devices. Each of these units performs a specific task. However, none of them can function independently on their own. They are logically related and controlled to achieve a specific goal. W hen they are thus integrated they form a fully fledged **computer system.
- 8 COMPONENTS OF A COMPUTER SYSTEM** The basic parts of computer system are: Input Unit The Central Processing Unit Output Unit Fig. 1.9 Central Processing Unit The Input Unit: Input dev ices are the dev ices which are used to feed programs and data to the computer. The input system connects the external environment with the computer system. The input dev ices are the means of communication between the user and the computer system. Typical input devices include the keyboard, floppy disks, mouse, microphone, light pen, joy stick, magnetic tapes etc. The way in which the data is fed into the computer through each of these devices is different. However, a computer can accept data only in a specific form. Therefore these input devices transform the data fed to them, into a form which can be accepted by the computer. These devices are a means of communication and inter^1 station between the user and the computer systems. Thus the functions of the input unit are : accept information (data) and programs. convert the data in a form which the computer can accept. provide this converted data to the computer for further processing.
The Central Processing Unit:
This is the brain of any computer system. The central processing unit or CPU is made of three parts:
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The control unit. The arithmetic logic unit Te primary storage unit The Control Unit : The Control Unit controls the operations of the entire computer system. The control unit gets the instructions from the programs stored in primary storage unit interprets these instruction an subsequently directs the other units to execute the instructions. Thus it manages and coordinates the entire computer system. The Arithmetic Logic Unit: The Arithmetic Logic Unit (ALU) actually executes the instructions and performs all the calculations and decisions. The data is held in the primary storage unit and transferred to the ALU whenever needed. Data can be moved from the primary storage to the arithmetic logic unit a number of times before the entire processing is complete. After the completion, the results are sent to the output storage section and the output devices. The Primary Storage Unit: This is also called as Main Memory. Before the actual processing starts the data and the instructions fed to the computer through the input units are stored in this primary storage unit. Similarly, the data which is to be output from the computer system is also temporarily stored in the primary memory. It is also the area where intermediate results of calculations are stored. The main memory has the storage section that holds the computer programs during execution. Thus the primary unit: Stores data and programs during actual processing Stores temporary results of intermediate processing Stores results of execution temporarily 1.8.3 Output Unit: The output devices give the results of the process and computations to the outside world. The output units accept the results produced by the computer, convert them into a human readable form and supply them to the users. The more common output devices are printers, plotters, display screens, magnetic tape drives etc.
Check your Progress - 1. 7 & 1. 8
1. Fill in the blanks. a. The primary storage unit is also called as ………………… b. Arithmetic logic unit is a part of ………………………… c. The unit of the computer which gives t h e results of the process and computations is the …………… 2. Answer in brief a. Define a system. .............................................................................................................................. .............................................................................................................................. b. W rite the functions of the input unit. .............................................................................................................................
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to store the data and produce the results on the basis of detailed step by step instructions given to it b) Software is a collection of programs which utilize and enhance the capability of the hardware. It consists of the various computer programs, procedures and other documentation used in the operation of a computer system. 1.
1. a- (iii) b- (iv) c - (i) d- (ii) e- (v)
a) True b) False c) True d) True e) False 1. 3
- a) Microcomputer b) Hybrid Computer c) Digital
- a) Multiple processors multiple instructions at the same time. This is known as parallel processing. b) Analog computer is a computer in which data (information) is recognized as a continuous measurement of a physical property like voltage, speed, pressure etc. Graphical output or readings on a dial are obtained, ex. voltage, speed, temperature, pressure can be measured in this way. c) Mainframe computers are very large computers which process data at very high speeds. They can be linked into a network and are used in large organizations and government departments, ex. IBM 4381. 1. 4 & 1. 5 1 a) - ii) speed 2 a) Applications of modern day computers : Scientific, Engineering and Research : They are used in areas which require lot of experiments, mathematical calculations, weather forecasting, and complex mathematical and engineering applications. b) Limitations of computers : Computers can only do what they have been programmed to do. They can execute only those jobs that can be expressed as a finite set of instructions to achieve a specific goal where each step has to be clearly defined. 1. 1. a) - i) input device b) - iii) central Processing unit 1. 7 & 1. 8
a) Main Memory b) Central Processing Unit c) Output Unit
a) A system is defined as a group of integrated parts which are designed to achieve a common objective. Thus, a system is made up of more than one element or part, where each element performs a specific function and where all the elements (parts) are logically related and are controlled in such a way that the goal (purpose) of the system is
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achieved. b) The functions of the input unit are : i) Accept information (data) and programs. ii) Convert the data in a form which the computer can accept. iii) Provide this converted data to the computer for further processing. 1. 11 QUESTIONS FOR SELF - STUDY
- Define the terms: data, program, hardware and software.
- List and explain in brief the characteristics of computers.
- Define a System. W hat constitutes a computer system?
- W rite short notes on Fourth Generation of Computers, Limitations of computers.
- Explain the classification of computers on the basis of their capacity to access memory and size.
- List the applications of computers. 1. 12 SUGGESTED READINGS
Computer Fundamentals
Concepts, Systems & Applications – P.K Sinha
REFERENCE
http://www.tutorialspoint.com/
Input Devices and Output Devices / 19 Chapter- 2
Input Devices and Output Devices
**2. 0 Objectives
- 1 Introduction
- 2 Input Devices
- 3 Output Device
- 4 Summary
- 5 Check Your Progress -** Answers 2. 6 Questions for Self - Study. 2.7 Suggested Readings After studying this chapter you will be able to: Explain the definitions of peripheral devices. Describe different types of input dev ices like punched cards, keyboards, mouse, digitizers and scanners and output devices like printers, plotters, video display terminals and microfilms, their broad design, their features advantages and disadvantages. Discuss the common peripheral devices, their physical appearances and the mode of operation of these dev ices. The student would be able to use these devices in the practical efficiently. As seen earlier, computer hardware is made up of the physical parts of the computer system like the electronic ICs, magnetic storage media and the mechanical devices. The devices which are a means of communication between the computer and the outside world are called as peripheral devices. Those peripheral devices which supply information i.e. data and progr ms from the outside world to the computer are the input devices. Those peripheral devices which give information from the computer to the user or store them in secondary storage devices, like floppy disks or tapes for future use are called output devices. The processors which are required to convert the input data into machine readable form and to convert the output generated by the computer into human readable form are known as input/output (I/O) interfaces. There are two concepts related to the way in which data is input to the computer:
1. On-line Data Input : Here data is directly transferred to the computer 2. Off-line Data Input : - Here the data is not immediately transferred to the computer. **The various types of input devices most commonly used are :
- 1 Punch Cards :** Data is recorded onto punch cards or punch tapes using standard codes, like the Hollerith code. The pattern of these holes is interpreted by a card reader device and converted into machine readable form. A punch card machine is used to transcribe the data onto the card. 2.2 INPUT DEVICES **2.1 INTRODUCTION
- 0 OBJECTIVES**
Computer Fundamentals / 20 Fig. 2. 1 Punch Card and a Keyboard Characteristic of punch card they are cheaper they are reliable. Disadvantage of punch card The major drawback of these cards is that they cannot be reused. Also the cards have to be handled and stored carefully. Even if a single card is misplaced or the arrangement of the cards gets disturbed it becomes very difficult to rearrange them and to detect there problem. Punched cards require large storage space since they cannot be folded. 2. 2. 2 Keyboard The keyboard is one of the most commonly used input device. The computer keyboard is similar to a typewriter keyboard. The keyboard has keys made up of letters, numbers, symbols and special function keys. A display screen or monitor (Cathode Ray Tube) is used to display the data entered by the operator with the keyboard. This monitor can also display the results of processing as well as messages generated by the computer. A special symbol, called a cursor, indicates the position on the screen. There are special keys on the keyboard which allow the cursor to move in up, down, left and right directions. Other special keys on the keyboard include keys like Tab, Del, Ctrl, Ins, PgUp, PgDn etc. The keys on the keyboard include : A-Z : Used to enter alphabets 0 - 9 : Used to enter numbers Up, Down, Left, Right(Arrow Keyes): To Move the cursor in the specified direction F 1 - F 12 : Special Function Keys PgUp/PgDn : To move cursor up or down by one page enter: To move cursor to a new line Shift : A Special key To Select the other option shown normal character on the same key Num Lock : Activates the keypad on the right side of the keyboard. In the normal mode this numeric pad works as per the function written below the number on the key Advantages of the keyboard : It is very easy to use a keyboard It offers a number of facilities Editing or changing the input data is very easy with the help of the keyboard It is relatively Inexpensive 2. 2. 3 Mouse The mouse is a pointing device. The mouse is used to control and manipulate cursor movement on the monitor. The mouse usually has three or four buttons on it and a roller ball which signals the movements made by the mouse on a flat surface. These movements are transferred to the system. The mouse is rolled on a flat surface by the user. It can be used independently, but normally it is used in conjunction with the keyboard to improve the efficiency of the input operation. The mouse can be used to select data. Also the mouse makes it possible to move fast from one par of the screen to the other. The various types of mouse in use are Mechanical mouse
