Computer Concepts

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

COMPUTER CONCEPTS INTRODUCTION No other technology has made such a rapid growth and change in science and technology in a short duration of time as the computer technology. Computers have a become a part and parcel of every human beings life. One can imagine the power and position of computers by looking into the statements “By the year 2099, there will be no clear distinction between humans and machines, we will have merged". Within the next 20 years, computers will be powerful like our human brain. Though computers by themselves have no intelligence and do not have the ability to learn, they have created situations that make us feel as if computers are better than human beings. In some ways, computers are fast, store large volumes of data and are more efficient than human beings. Computers are largely self-directing i.e. they have the ability to follow the set of instructions given to them (of course, by human beings!)Without human interaction. With limited intelligence, limited language capability (understands only programming languages) computers continue to dominate in the field of science and technology. The computers have emerged as a result of countless ideas inventions and developments made by different people throughout this century.

OBJECTIVES After studying this unit you should be able understand computer capabilities, functional blocks of a computer the difference between data and information, speed and accuracy capabilities. How data is manipulated.

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

NEED FOR COMPUTER LITERACY A few decades ago, a few computers in existence were very huge and expensive; they were usually used for scientific purposes and thus had little impact on the lives of common people; only a few people had the knowledge of computer capabilities and limitations. But over the period the scenario has changed. Millions of computers ranging from small micro-sized units to super-computers are found in offices, factories, schools, homes, hospitals, banks, retail stores and almost everywhere. Let us take a few examples and look at the use of computers a) Travel arrangements for a trip: An efficient computer controlled airline reservations system keeps track of available seats and quickly records the reservation. b) You went to a hospital for physical checkup: If the exam is for insurance purposes, your medical history and the doctors finding will be forwarded to the insurance company where they are stored in a large computer data bank. c) Visit to a supermarket: When you go to a supermarket you can find several computers, which read the codes (like bar code) on the products and prepares the cash bills within a few minutes. There is no need for the customer to wait for a long time to get his bill. By looking at the typical sample examples listed above, the presence of computers in your daily life cannot be ignored or under estimated. Computers can have both good and bad effects on the individuals. Computer applications will expand greatly in the years to come. There will be vast potential for widespread benefits as well as undesirable side effects. Educated citizens should not rely solely on computer specialists to prevent the possible dangers and bring about the positive potential. Rather, citizens should learn about computers so that they can reap the benefits and they can insist the designers of ill-conceived computer systems to assume the responsibility for effects these systems have on people.

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

The following are the areas of knowledge required for computer literacy:

1. Computers themselves: You should understand the organization, capabilities and limitations of the various machines or hardware that make up a modern computer system. 2. What computers do: You should be familiar with some of the most common applications of computers in today's society. 3. How computers are put to work: You need to know the analysis, design and program preparation procedures that must be carried out in order to produce software. Basic knowledge of hardware is also very essential. 4. The social impact of computers at work: Finally you should know how individuals and organizations may be affected by present and future computer applications.

COMPUTER SYSTEM ORGANIZATION INTRODUCTION

Let’s take a look at our computer definition. A computer is a fast and accurate symbol manipulating system that is organized to accept, store, process and produce results under the direction of a stored program of instructions. This section explains the computer is a system and how a computer system is organized. Organization of computers input devices, Keyboard, mouse and classification of Computers.

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

THE SYSTEM CONCEPT

The system is a group of integrated parts that have the common purpose of achieving same objectives. The following characteristics are important: 1. A group of parts: A system has more than one element. A steel ball is not a system but it might be part of a bearing assembly that could be combined with other components to produce an irrigation system. 2. Integrated parts: A logical relationship must exist between the parts of a system, mechanical and electronic systems such as washing machines and video games have components that work together. And a personal management system may consist of integrated procedures for recruiting training and evaluating employees. 3. Common purpose of achieving objectives: The system is designed to accomplish one or more objectives; all system elements should be controlled so that the goal is achieved. Totally automated systems have highly controlled operations, systems operated by people sometimes get out of control. A computer is a group of integrated parts that have the common purpose of performing the operations called for in the program being executed it is also a system. Any system may be comprised of smaller systems or subsystems.

A subsystem

is a smaller system contained within a larger one. The component parts found in most computer system ex: printers are systems in a way and computers in small may be considered subsystems in larger super systems such as air traffic control system.

ORGANIZATION OF COMPUTER SYSTEM Input Devices

central processing unit

output devices

Fig. 1 Overview of Processing

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

The figure above shows the basic organization of computer system. The system included input, processing and output devices. Let us see each component of the system in more details.

INPUT DEVICES

Computer systems use many devices for input purposes. Some allow direct human/ machine communication. The keyboard of a workstation connected directly to or online to a computer: Devices that read data magnetically recorded on specially coated plastic tapes or floppy plastic disks are popular. Regardless of the type of device used, all are components for interpretation and communication between people and computer systems.

KEYBOARD Is the friendliest input device through which data programs are keyed in and certain commands to software can be given from the keyboard. The keyboard consists key switches there is one key switch for each letter, symbol number etc. much like a typewriter when a key is pressed, the key switch is activated. The keyboard has an electronic circuit to determine which key has been pressed. Then the 8-bit binary code is generated and sent to the computers. The binary code may be an ASCII (American Standard Code for Information Interchange), EBCDIC (Extended Binary Coded - Decimal Interchange Code) or Hex code.

Computer Keyboard

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

Keyboards are classified into two types depending on the number of keys present in them. a) Ordinary Keyboard: consists of 86 keys. b) Extended Keyboards: consists of 101 keys ( Windows ready )

Keyboards are of two types based on the fashion of data transfer. a) Serial Keyboard: It sends the data, bit by bit in a serial fashion and the computer converts the data into a parallel type. b) Parallel Keyboard: It sends the data as a byte in parallel form, the bits are sent simultaneously on different lines (wires). Mouse: A mouse is a graphical input device the term mouse is used because of its shape. The mouse has two or three buttons on its top. The function of each button is defined by the software. The mouse also has a small rotating ball at the bottom. When the mouse is moved on a rubber pad, the ball rolls whose movement is converted into an electrical signal and seat to the CPU on the CPU this movement is interpreted and displayed on the screen of the monitor (CRT) in the form of movement of the arrow mark. This movement of arrow mark is used to highlight the graphical index on the screen. When a desired command shown on the screen is approached by the arrow mark due to the movement of the ball in the mouse the click button is pressed to highlight the same.

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

There are 2 methods by which a mouse is connected to a computer serial interface and parallel interface.

CENTRAL PROCESSING UNIT (CPU) The heart of any computer system is the CPU. Three main sections are generally located within computers of all sizes. a) The Primary Storage Section: This section is used for four purposes. 1. Data are fed into an input storage area where they are held until ready to be processed. 2. A working storage space that holds the data being processor and the intermediate results of such processing. 3. An output storage area holds the finished results of the processing operations until they can be released. 4. In addition to these data-related purposes, the primary storage section, also certain program storage area that holds the processing instructions. In addition to primary memory storage or main memory section most computers also have secondary storage capabilities ( like hard disk, floppy disk ) b) The arithmetic – logic section: All calculations are performed and all comparisons (decisions) are made in the arithmetic – logic section of the unit are temporarily placed in a designated working storage area until needed at a later time data may thus move from primary storage to the secondary storage many times before the processing is finished. Once completed, the final results are released to an output storage section and from there to an output device.

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

c) Control Section : The control section maintains order and directs the operation of the entire system. Although it does not perform any actual processing on the data, the control unit acts as a central nervous system for the other components of the computer. At the beginning of processing, the first program instruction is selected and fed into the control section from the program storage area. There it is interpreted, and from their signals are sent to other components to execute the necessary actions.

OUTPUT DEVICES Output devices: - Like the input devices, output devices are instruments of interpretation and communication between humans and the computer system. Printer is Considered as output device. All input/output and secondary storage units are sometimes called peripheral devices.

COMPUTER LIMITATIONS Computers although they are very useful, they have some limitations. i) Programs must be reliable: As a machine, the computers do what it's programmed to do and nothing else. This doesn’t mean that it must be stupid clever programs can be written to direct the computers to store the results of previous decisions. But a seemingly flawless program that has operated without a problem for months can suddenly produce non-sense. A reliable program that’s supplied with incorrect data may also produce non-sense. ii) Application logic must be understood: The computer can only process applications which can be expressed in a finite number of steps leading to a previously defined goal. Each step must be specifically and clearly define, if the steps in the problem solution cannot be precisely stated, the job cannot be done. The computer may not be of much help to people in areas where qualitative material or evaluation is important. 8

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

For example, The market decision may be of a qualitative nature because sales volume data may rest on future social, political, technological and economical events. However, the computer can let the manager know how the product will fare under assumed price, cost and sales volume condition. iii) Applications must be suitable: Writing programs is a human task it can be time consuming and expensive. Thus, nonrecurring jobs are often not efficient areas for business data processing applications. Rather as a general rule its most economical to prepare business programs for large-volume, repetitive applications such as payrolls that will be used many times.

CLASSIFICATION OF COMPUTERS Computers are classified by the type of data they are designed to process. Data may be obtained either as a result of counting or through the use of same measuring instrument. Data that are obtained by counting are called discrete data; examples of discrete data are total number of students in a classroom. Data that must be obtained through measurement are called continuous data. For example, of continuous data is the speed of an automobile measure by speedometer or the temperature of a patient as measured by a thermometer. DIGITAL COMPUTER is a counting device that operates on discrete data. It operates by directly counting members (or digits) that represent numerals, letters or other special symbols. Just as digital watches directly count off the seconds and minutes in an hour, digital processors also count discrete values to achieve the desired output results. In contrast to digital processors, however, there are also analog machines that do not compute directly with numbers. They deal with variables that are measured along a continuo scale and are recorded to some predetermined degree of accuracy. Temperature for example may be measured to the nearest tenth of a degree on the Celsius scale, voltage may be measured to the nearest of hundredth of a volt. A service station petrol pump may contain analog processor. ANALOG COMPUTERS may be accurate to within 0.1 percent of the correct value. But digital computers can obtain whatever degree of accuracy is required simply by calculating 9

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

additional places to the right of the decimal point. For example; A pi(π ) has a value of 3.1416. Actually the true value of pi is 3.14159.... (This number could go on for pages) Desirable features of analog and digital machines are sometimes combined to create a hybrid computing system in a hospital intensive-care unit, for example analog devices may measure a patient’s heart function, temperature and other vital signs. These measurements may then be convicted into members and supplied to a digital component in the system. Classification of computers based on their size, cost & configuration. In this category computers are classified as micro-computers, mini computers, main frame computers, home computers and super computers.

MICRO COMPUTERS: A Micro computer is the smallest general-purpose processing system that can execute program instructions to perform a wide variety of tasks. The important features of micro computers are: 1. Micro computers are known as home computers, personal computers, desktop computers and small business computers. 2. These are small, low-cost digital computer with a micro processor as its CPU, a memory unit an input device and an output device. 3. The word length of a micro-computer lies in the range of 8-32 bits. 4. CPU’s are in a single chip 5. Storage capacity is small 6. Applications include general-purpose calculations, industrial control, office automation etc.

PERSONAL COMPUTERS (PC’S): Personal computers are micro-computers for general-purpose computations. These are classified as PC, PC/XT, PC/AT and super AT (or super micro) based on their cost and

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

configuration. All these types contain a CPU, RAM, ROM, CRT display, Keyboard and secondary memory. Features: 1. PC is the simplest and cheapest type of computer and it uses an INTEL 8088 ( micro processor chip) as CPU, 640 KB, RAM, 8KB ROM ( ROM can be extended up to 64 KB) and floppy disk as secondary memory; processing speed of a PC lies in the range 1-5 MIPS ( micro-instructions per second ) 2. PC/XT (Personal computer extended technology) contains hard disk, floppy disk drives (360/1.2 MB), Intel 8088 CPU, 640 KB RAM and 8 KB ROM. This is costlier than a PC because of the hard disk it contains. PC/XT is a single user system. Processing speed of a PC lies in the range 1-5 MIPS and hard disk capacity lies in the range 20-80 MB. 3. PC/AT (Personal computer advanced technology) contains. Intel 80286 as CPU, 640 KB RAM (expandable to 4 MB), 64 KB ROM (expandable to 128 KB), hard disk drive and floppy disk drive (360 KB/1.2 MB), its CPU is powerful than the CPU of PC/XT and four to five terminals can be connected to it to make it multiuser. Processing speed of PC/AT lies in the range 1-5 MIPS and hard disk capacity lies in the range 20-80 MB. 4. Super AT (or super micros) uses a 32-bit CPU, Intel 80386 & 80486. The RAM capacity of super macros lies in the range 2-8 MB in 80386 CPU can be extended up to 32 MB and in case of 80486 up to 64 MB. The hard disk capacity of super macro lies in the range 200 –800 MB. The processor speed of 80386 CPU lies in the range 3-5 MIPS and that of 80486 CPU is 12 MIPS to 25 MHz clock UNIX is used as operating system. The processing speed of home computers and microcomputers for industrial control is less than 1 MIPS. Home computers are used for entertainment, basic education and home management and income tax calculation, investment analysis etc.

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

MINI COMPUTERS: The salient features are:1. The word length is 32 bits and their processing speed lies in the range 10-30 MIPS. 2. RAM capacity lies in the range 8 MB – 96 MB ( in same it can be extended up to 128-256 MB) 3. The hard disk capacity lies in the range 380 MB – 2GB ( gig bytes) 4. Most mini-computers use Motorola 68030 and 68040 CPU. The Minicomputers which are faster and more powerful than microcomputers can support upped 64 or even 100 terminals and some minicomputers are Uni. Processor and some others are multi processor systems. These are used for payroll preparation and scientific computation, multi-user and interactive applications in college universities research organizations, industries, sophisticated real time (industrial) control, interactive engineering design work etc..

Examples of mini computers are:

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

IBMAS/400/B60



VAX8842(VAX stands for Virtual address)



Extension - VAX computers are manufactured by Digital Data Corporation)



WIPRO S – 68030V & S-6833V built around 68030 CPU



WIPRO LANDMARK 860 ( a super mini) built around Intel i860-CPU



HP 9000 series 800 ( super mini) built around Hewlett Pacard’s VLSI RISC processors



HCL magnum built around 68030 CPU and 68040 CPU.

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

MAIN-FRAME COMPUTERS The mainframe computers are faster and more powerful than mini computers. These computers are used where large amount of data are to be processed or very complex calculations are to be made and these tasks are beyond the computing capacity of mini computers. The main features are: 

The word length may be 48, 60 or 64 bits.



Memory capacity range is 64-256 MB and hard disk capacity is 1000 MB – 10 GB or more.



Processing speed lies in the range 30-100 MIPS.

The mainframe computers are used in research organizations, large industries, business organizations, government organizations, banks and airline reservations etc. Example: IBM 4300 series  IBM 308X series  Latest model IBM 3090 series  IBM 9000 series  HP 9000 series 8705/400  HP 9000 model 8705/300

SUPERCOMPUTERS: The salient features are: 1. Their word length is 64-96 bits; memory capacity is 256 MB & more; hard disk capacity 1000 MB and more 2. Processing speed lies in the range of 400 MIPS – 10000 MIPS. In a single machine cycle tow 64 – bit data can be added

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

Super computers are much faster and more powerful than mainframe computers. Super computers are specially designed to maximize the number of FLOPS ( Floating Point Operations Per Second). Their FLOPS rating is usually more than igiga flops per second. A super computer contains a number of CPU’s which operate in parallel and make it faster. They are used for massive data processing & solving very sophisticated problems. They are used for weather forecasting weapons research and development, rocket launching, seismology, atomic, nuclear and plasnia physics. Example: CRAY – X – MP/14, X-MP/24 & X-MP/48  CRAY – MP, CRAYZ, CRAY3, CRAY Y-MPC  ETA 10 ( Developed by control data Corporation )  SX – 2 (Developed by Nippon Electric Corporation, Japan)  SX – 3R ( 25.6 GIGA FLOPS )  HITACS – 300 ( 32 GIGA FLOPS, HITACHI MAKE )

COMPUTER CAPABILITIES Most people are aware that a computer is a machine that can perform arithmetic operations, but it is much more than just an arithmetic number crunching device. It is also a machine that can choose copy, move compare and perform various non-arithmetic operations on many alphabetic, numeric and other symbols that humans use to represent things. The computer manipulates these symbols in the desired way through a sequence of instructions, called a program. A program is a detailed set of human instructions that directs the computer to function in a specific way to produce a desired result. Electrical or electromechanical components are known as hardware.

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION •

CAM (MBA-1st Sem)

SPEED AND ACCURACY CAPABILITIES:

A computer works one step at a time. It can add, subtract, compare digits and, letters, move and copy numbers and letters. There's nothing profound in these operations. What's significant is the computer speed. This speed is measured as milliseconds, microseconds, nanoseconds and pico seconds (Recent study says computer speed is being doubled every six months). The speed required for computers to execute a basic operation like addition varies from a few microseconds for the smallest machines to 80 nano seconds or less for the larger ones. Thus, the slowest computers can perform hundreds of thousands of additions in a second while the largest systems can compute several million additions in the same period. In addition to being very fast, computers are also very accurate. It is estimated that you or I would make one error in every 500 to 1,000 operations with a calculator. But the circuits in a computer require no human interaction between processing operations and have no mechanical parts to wear out and malfunction. Thus these circuits can perform hundreds of thousands (or millions) or operations every second and can run errorless for hours and days together at a time. Beyond this, computers also have built-in self-checking capabilities that permit them to monitor the accuracy of their internal operations. If the input data are correct and relevant, and if the program of processing the instructions is reliable, then the computer can generally be expected to produce accurate output. The phrase “Garbage in, Garbage-out" or GIGO is used often by people who work with computers to illustrate the importance of input data and correct instruction.

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DATA MANIPULATING CAPABILITY:

The first computers were built to manipulate numbers in order to solve arithmetic problems. Along with numbers we also use alphabets and different symbols in our daily life. Luckily, early computer experts made the important discovery that a machine that can accept, store and process numbers can also manipulate non-numeric symbols. Manipulating these familiar symbols is possible if an identifying code number is assigned to the symbol to be stored and processed. Thus, the letter A can be represented by a code, as can the letter B, the addition

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

symbol and so on. Of course, one must give the computer instructions for it to manipulate the coded and stored symbols in a desired way.

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DATA - VERSUS - INFORMATION:

The word “data" is the plural of datum, which means fact. Data then, are facts or raw material of information. Data are represented by symbols. Information is data arranged in ordered or useful form. That is information is relevant knowledge produced as output of data processing operations and acquired by people to enhance understanding and to achieve specific goals. The following schematic representation shows you the processing of raw data to provide information: Data input Collection

Raw data processing

•

Data and actions

Information

End user decisions

DATA PROCESSING ACTIVITIES:

Data processing consists of gathering the raw data input, evaluating and bringing order to it and placing it in proper perspective so that useful information is produced. All data processing, whether done by hand or computer system consists or three basic activities: capturing the input data, manipulating the data and managing the output results. i)

Capturing the input data:

Data must be originated in some form and verified for accuracy prior to further processing. They may initially be recorded on paper source documents and then converted into a machine - usable form processing or they may be captured directly in paperless machine-readable form. ii) Manipulating the data: 16

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

One or more of the following operation may have to be performed on the data that is collected. 1. Classifying: Organizing items with like characteristics into groups or classes is called classifying. Data taken from a materiel stores sales bill for example, may be classified by product sold, Sales department sales person, or any other classification useful for store management.

Classifying is usually accomplished by assigning pre-determined

abbreviation codes to the items being arranged. The three types of codes used are numeric, alphabetic and alphanumeric. 2. Sorting: Usually it’s easier to work with data if they are arranged in a logical sequence. For example: include first to last, biggest to smallest oldest to newest.

Arranging

classified data in such a sequence is called sorting. 3. Calculating: Arithmetic manipulations of the data is called calculating. For example: In calculating a sales person's pay, the hours worked multiplied by the hourly wage rate gives the total earnings.

Payroll deductions such as taxes are then calculated and

subtracted from total earnings to arrive at the sales person's take-home pay. 4. Summarizing: Reducing masses of data to a more concise and usable form is called summarizing. Example: the general manager of a retail store is interested only in a summary of the total sales of each department. A summary report would give only total sales information. Department managers may want more detailed information such as the total sales of each department broken down into sales by product type and by sales person.

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MANAGING THE OUTPUT RESULTS:

Once the data have been captured and manipulated, one or more operations may be needed. i) Storing and retrieving: Retaining data for future reference in storing, storage media such as paper ( in sheet, punched card or punched tape form), microfilm, or magnetic disks and tapes are generally used. Recovering stored data and / or information is the retrieving activity. One slow approach is for people to search file cabinets. A much faster method is to use 17

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

electronic enquiry devices that are connected directly to a computer and mass storage unit containing the data. ii)

Communicating and reproducing: Transferring data from one location or operation to another for use or for further processing is data communication a process that continues until information in a usable form, reaches the final user. Some times of course, its necessary to copy or duplicate data. This reproduction activity may be done by hand or by machine.

COMPUTER CONCEPTS There's nothing new about the data processing steps just stated above. They have been performed down through the ages, first by hand, and then by machine assisted manual and electromechanical punched card methods and now by computers.

The four functions which follow are all that a computer can perform but they also include most data processing steps: i)

Input / Output operation: A computer can accept data (input) from and supply processed data (output) to a wide range of input/ output devices. Such devices as keyboards and display screens make human - machine communication possible. Multiple output documents may be reproduced by printers.

ii)

Calculation operations: The circuits in a computer are designed to permit addition, subtraction, multiplication and division.

iii)

Logic/ Comparison operation: The computer also has the ability to perform certain logic operations. For example, when two numbers represented by the symbols A and B are compared, there are only 3 possible outcomes: 1) A is equal to B ( A=B); 2) A is greater than B (A>B) or 3) A is less than B (A
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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

The computer is able to perform a simple comparison and then, depending on the result, follow a predetermined branch or course of action in the completion of that part of A and B work (see figure below)

A is Compared With B A
A>B

A=B

Fig 1 Possible outcome when A is compared with B

This comparison ability makes it possible to classify item A is having or not having the characteristic of B. This simple ability to compare is an important computer property because more sophisticated questions can be answered by using combinations of comparison decisions. iv)

Storage and retrieval operations: Both data and program instructions are stored internally in a computer. Storing both data and instructions in same memory is known as stored program concept or John Von Neumann Concept. And once stored, both may be quickly called or retrieved for use. The time required for data to be retrieved is measured in micro-or nanoseconds.

v)

TYPICAL PERSONAL COMPUTER CHARACTERISTICS Some of the major characteristics of a typical personal computer are summarized below. This should give a glimpse of a desktop computer and introduce you to some of the terms used with personal computer. 19

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

FEATURE CPU type

Bus type

BIOS manufacturer

CPU Speed

Video board

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CAM (MBA-1st Sem)

TYPICAL BRIEF DESCRIPTION 8088, 80286, 80386, 80486, The CPU determines how Pentium-I, II, III much memory the system can address, what kind of software it can run, and how fast it can go PC Bus (8-bit ISA), AT Bus The bus determines what (16-bit ISA), Proprietary kind expansion circuit 32-bit Micro Channel, boards will work in the EISA, Local or VESA bus, machine. Most buses are PC-Card, PCI incompatible with the others (exception: EISA bus computers can use ISA cards), which makes it important that you know which kinds of boards you’re buying American Megatrends, Inc BIOS (Basic Input/Output (AMI), IBM, Compaq, System) are the low-level Phoneix, Award system software that determines how compatible your computer is. 4.77 MHz (PC speed) upto Megahertz (MHz) is a 200 MHz rough measure of system speed. All other things being equal, a 10 MHz machine is faster than a 5 MHz machine. (All other things generally aren’t equal) Monochrome Adapter The video board affects (MDA), Color/Graphics what kind of software you Adapter (CGA), Enhanced can run and how quickly Graphics Adapter (EGA), data can get on the screen. Video Graphics Array It can be easily changed, (VGA) 8514 Adapter, and the oldest PC can use Extended Graphics Array anything from a (XGA), Diamond Viper monochrome board up to a ATI Mach 32. VGA or 8514. Changing video boards may require updating software to use those video boards. Video boards vary by the number of colors and pixels (the

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

dots on the screen) that they can display. Most important in modern video boards, however, is whether they hold video data as a simple “Dumb frame buffer” which requires that the CPU must do all the video work, or contain circuitry that can help with the grunt work of graphical screens: boards like that are said to be “bitblitter” boards. Parallel port Unidirectional, Bi- The parallel port acts as directional, EPP (Enhanced the basic interface for Parallel Port) printers. In its simplest form, it’s unidirectional. More modern parallel ports may support bi-directional data flow, or may even support higher speeds of data transportation, known as an Enhanced Parallel Port, usually abbreviated EPP. Bi-directional parallel ports are more and more essential in order to support newer printers, which work their best when teamed with a bidirectional or, better, EPP port. Serial port UART 8250, 16450, 16550 The UART is the main chip around which a serial port or internal modem is built. The 16550 UART is the fastest of the lot, and is essential for high speed communications and communications in multitasking environments. Amount of 640K - whatever There are several kinds of memory memory or RAM (Random Access Memory) conventional, extended, 21

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AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

and expanded. They all solve different problems. Some software won’t run without a particular amount of one or more of these kinds of memory. Most PCs come with 64 or 128 MB of RAM.

22

System Clock / Calendar

Built on motherboard or added on expansion board.

Hard disk interface

ST506/412, ESDI, SCSI, IDE, EIDE

Hard disk encoding scheme

MFM, RLL, ARLL

Keyboard type

XT-type, AT-type

Floppies

5.25 inch 360 K, 1.2MB,

Again, not terribly important. Machines with built in clocks usually have DIS support to directly read from or modify the time and date. Others must run a separate program. What method does the hard disk controller (a circuit card in the system) use to talk to the hard disk? This affects speed and can be easily changed in most systems. Modern systems use IDE or SCSI; SCSI is preferable for its flexibility. How much data is squeezed on to the area on disk called a track? These methods are used to squeeze more data onto a hard disk, and can easily be changed. IBM originally put a keyboard control chip in the keyboard for the PC and XT. They moved it to the motherboard for the AT, so you’ve got to know which kind of keyboard interface you’ve got. Most clone keyboards have a switch allowing them to swing both ways. What kind of floppies will

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

23

COMPUTER ORGANISATION supported

720K (Unusual); 3.5 – inch 720K, 1.44 MB, 2.88MB

Number of expansion slots

3-10

Configuration method

Switches configuration (CMOS) memory

Number of interrupts (IRQ levels) supported Number of DMA (Direct Memory Access) channels supported Sound Card

8 or 16

SCSI host adapter

SCSI-I or SCSI-II single ended or differential; normal, fast, wide, or fast/wide

4 or 8

8 or 16 bit FM, MIDI, and/or wavetable Audio interface

CAM (MBA-1st Sem)

your machine support? This can be changed fairly easily. The more, the merrier. Many bit-name computers only sport three expansion slots; look instead for the eight-slot models. Computers won’t work until you tell them about themselves, or configure them. It’s done with either physical switches or software. Affects the number and type of expansion boards in a system. Affects the number and type of expansion boards in a system. Sound boards support music and sound reproduction on your PC, but music and sound are represented in either an 8bit or a 16-bit format. 16bit is better, but takes more space. The sounds are recorded and reproduced either with FM synthesis, MIDI control, or wavetables. Additionally, a sound card in combination with a CDROM can play music on your PC, with the right audio interface cable. SCSI is a kind of universal hardware interface that allows you to put hard disks, CD-ROMs, tape drives, optical drives, and scanners onto your machine with a minimum of hookup trouble. SCSI is

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

24

COMPUTER ORGANISATION

LAN board

Ethernet, Token Ring and ARCNet

CD-ROM Drive

Spin speed (internal or external) SCSI, IDE or proprietary interface

Printer Control language

Epson codes, HPPCL (Laser jet commands) Post

CAM (MBA-1st Sem)

still an evolving standard, but with many choices Most PCs don’t have SCSI, but most could benefit from adding SCSI; all you need is the SCSI host adapter board and some software. Local area networks (LANs) allow PCs to communicate with one another, share data and printers. Each PC on a LAN needs a LAN transceiver card, and there are three types: Ethernet, Token Ring, and ARCNet. Ethernet is the most common. Most businesses have LANs, and more and more homes are adding LANs as they acquire PCs. support CD-ROM disks, which can hold almost 700 MB of data. More and more software ships solely on CD-ROM, making this item a necessity. They vary largely by whether they’re internal or external, and how quickly they can transfer data to a PC. Transfer speeds range from 150K/s (“single spin”), 300K/s (“double spin”), 450 K/s (“triple spin”), to 600 K/s (“quad spin”), 900 K/s (“six speed”). 1200 K/s (“eight speed”, 1500 K/s (“ten speed”) CDROM interface either by way of IDE or a SCSI host adapter or by way of a proprietary adapter. Printer control languages tell your printer how to

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION Script others.

CAM (MBA-1st Sem)

underline words, put pictures on the page, and change typefaces.

CHARACTERISTICS OF COMPUTERS SPEED

The computer was invented as a high-speed calculator. This has led to many scientific projects which were previously impossible. The control of the moon landing would not have been feasible without computers, and neither would today's more scientific approach to weather prediction. If we want tomorrow's forecast today (and not in six months time) meteorologists can use the computer to perform quickly the necessary calculations and analyses. When making flight reservations we want to know well in advance of take-off that a seat will be available - if it is not, then we have time to make other arrangements. The ability to get answers fast enough so that one has time to take action on them (or to make alternative plans, as in the case of airline reservations) makes real-time computing possible.

Electrical pulses travel at incredible speeds and, because the computer is electronic, its internal speed is virtually instantaneous. We do not talk in terms of seconds or even milliseconds. Our units of speed are the microsecond (millionths), the nanosecond (thousand0millionths) and latterly even the picoseconds (million-millionths). A powerful computer is capable of adding together two 18-digit numbers in 300 to 400 nanoseconds.

STAGE

The speed with which computers can process large quantities of information has led to the generation of new information on a vast scale, in other words, the computer has compounded the information 'explosion'. How can people cope with it? We can't, but computers can. But where do they keep it all?

25

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AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

As a human acquires new knowledge, the brain subconsciously selects what it feels to be important and worth retaining in its memory, and relegates unimportant details to the back of the mind or just forgets them. In computers, the internal memory of the CPU is only large enough to retain a certain amount of information. It is therefore, impossible to store inside the computer the records, for example, of every Premium Bond and the names and address of their owners. All of this data is stored outside of the memory of the CPU, on auxiliary or secondary storage devices. Small sections of the total data can be accessed very quickly by the CPU and brought into the main, internal memory, as and when required for processing.

The internal memory (in CPU) is built up in 1 K or K modules, where K equals 1024 storage locations. Babbage's Analytical Engine would have been capable of holding 1000 numbers, each of 50 digits. Computers come in many sizes. Many small micro-computers have an 8 K or 16 K store whilst 'super computers', such as the CDS CYBER 205 may have up to 1024 K stores (i.e. 1024 * 1024 locations).

ACCURACY

In spite of misleading newspaper headlines, the computer's accuracy is consistently high. Errors in the machinery can occur but, due to increased efficiency in error-detecting techniques, these seldom lead to false results. Almost without exception, the errors in computing are due to human rather than to technological weaknesses, i.e. to imprecise thinking by the programmer, or to inaccurate data, or to poorly designed systems.

VERSATILITY

Computers seem capable of performing almost any task, provided that the task can be reduced to series of logical steps. For example, a task such as preparing a payroll or controlling the flow of traffic can be broken down into a logical sequence of operations, whereas comparing the tones of a turner with a Vermeer cannot. Yet the computer itself has only limited ability and, in the final analysis, actually performs only four basic operations:

It exchanges information with the outside world via I/O devices, It transfers data internally within the CUP, 26

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

It performs the basic arithmetical operations, It performs operations of comparison.

In one sense, then, the computer is not versatile because it is limited to four basic functions. Yet, because so many daily activities can be reduced to interplay between these functions, it appears that computers are highly ingenious. Programming is the craft or reducing a given problem into interplay between these few operations.

AUTOMATION

A computer is much more than an adding machine, calculator or check-out till, all of which require human operators to press the necessary keys for the operations to be performed. Once a program is in the computer's memory, the individual instructions are then transferred, one after the other, to the control unit for execution. The CPU follows these instructions until it meets a last instruction which says 'stop program execution'. When Babbage claimed that his Analytical Engine would be automatic, he meant that once the process had begun, it would continue without the need for human intervention until completion.

DILIGENCE

Being a machine, a computer does not suffer from the human traits of tiredness and lack of concentration. If 3 million calculations have to be performed, it will perform the 3 millionth with exactly the same accuracy and speed as the first. This factory may cause those whose jobs are highly repetitive to regard the computer as a threat. But to those who rely on a continuous standard of output, e.g., quality control in the refining of oil and other chemical processes, the computer will be seen as a considerable help.

COMPUTER LIMITATIONS

1. It must be check and repair from time to time. 27

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

2. It cannot function alone without help from human 3. It cannot think on its own 4. It only understand computer language to execute command Although above limitation are important, but a part of them following are also several other limitations of computers.

PROGRAMMED BY HUMAN: Though computer is programmed to work efficiently, fast and accurately but it is programmed by human beings to do so. Without a program, computer is nothing. A program is a set of instructions. Computer only follows these instructions. If the instructions are not accurate the working of computer will not accurate.

THINKING: The computer cannot think itself. The concept of artificial intelligence shows that the computer can think. But still this concept is dependent on set of instructions provided by the human beings.

SELF CARE: A Computer cannot care itself like a human. A computer is dependent still to human beings for this purpose.

RETRIEVAL OF MEMORY: A computer can retrieve data very fast but this technique is linear. A human being's mind does not follow this rule. A human mind can think randomly which a 28

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

computer machine cannot.

FEELINGS: One of the main limits in the computer is of feeling. A computer can not feel about some like a human. A computer cannot meet human in respect of relations. Human can feel, think and caring but a computer machine itself cannot. A computer cannot take place of human because computer is always dependent of human.

CLASSIFICATION OF COMPUTERS Computers exist in a wide range of sizes and power. The smallest are embedded within the circuitry of appliances, such as televisions and wrist watches. These computers are typically preprogrammed for a specific task, such as tuning to a particular television frequency or keeping accurate time.

PROGRAMMABLE COMPUTERS

Vary enormously in their computational power, speed, memory, and physical size. The smallest of these computers can be held in one hand and are called personal digital assistants (PDAs). They are used as notepads, scheduling systems, and address books; if equipped with a cellular phone, they can connect to worldwide computer networks to exchange information regardless of location.

LAPTOP COMPUTERS AND PCS

Are typically used in businesses and at home to communicate on computer networks, for word processing, to track finances, and to play games. They have large amounts of internal memory to store hundreds of programs and documents. 29

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

They are equipped with a keyboard; a mouse, trackball, or other pointing device; and a video display monitor or liquid crystal display (LCD) to display information. Laptop computers usually have similar hardware and software as PCs, but they are more compact and have flat, lightweight LCDs instead of video display monitors.

WORKSTATIONS

Are similar to personal computers but having greater memory and more extensive mathematical abilities, and they are connected to other workstations or personal computers to exchange data. They are typically found in scientific, industrial, and business environments that require high levels of computational abilities.

MAINFRAME COMPUTERS

Have more memory, speed, and capabilities than workstations and are usually shared by multiple users through a series of interconnected computers. They control businesses and industrial facilities and are used for scientific research. The most powerful mainframe computers, called supercomputers, process complex and time-consuming calculations, such as those used to create weather predictions. They are used by the largest businesses, scientific institutions, and the military. Some supercomputers have many sets of CPUs. These computers break a task into small pieces, and each CPU processes a portion of the task to increase overall speed and efficiency. Such computers are called parallel processors.

DEFINITIONS OF OPERATING SYSTEM 1) Also known as an "OS," this is the software that communicates with computer hardware on the most basic level. Without an operating system, no software programs can run. The OS is what allocates memory, processes tasks, accesses 30

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

disks and peripherials, and serves as the user interface. With an operating system, like Windows, the Mac OS, or Linux, developers can write code using a standard programming interface (known as an API). Without an operating system, programmers would have to write about ten times as much code to get the same results. Of course, some computer geniuses have to program the operating system itself. 2) The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers. For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop -- it makes sure that different program and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system. 3) OS is a control program that controls execution of programs to prevent errors and improper use of the computer. As such there is No universally accepted definition of operating system. The one program running at all times on the computer is the kernel. Everything else is either a system program (ships with the operating system) or an application program

OPERATING SYSTEMS CAN BE CLASSIFIED AS FOLLOWS:

✦

✦

MULTIPROCESSING: Supports running a program on more than one CPU.

✦

MULTITASKING: Allows more than one program to run concurrently.

✦

✦

31

MULTI-USER: Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.

MULTITHREADING: Allows different parts of a single program to run concurrently. REAL TIME: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

OPERATING SYSTEM GOALS:

     

Execute user programs and make solving user problems easier. Make the computer system convenient to use. Use the computer hardware in an efficient manner. OS is a resource allocator. Manages all resources Decides between conflicting requests for efficient and fair resource use.

MULTIPROGRAMMING: The simultaneous execution of two or more programs by a single CPU, usually achieved by carrying out several instructions from one program, and then rapidly switching to the next one.

Multiprogramming is needed for efficiency because:  Single user cannot keep CPU and I/O devices busy at all times.  Multiprogramming organizes jobs (code and data) so CPU always has one to execute.  A subset of total jobs in system is kept in memory.  One job selected and run via job scheduling.  When it has to wait (for I/O for example), OS switches to another job.

MULTITASKING: The ability of an operating system to run two or more tasks at once. With one processor you will not normally have more than one task using the processor at a given moment in time, but the tasks will be scheduled so that they can all appear to be running at the same 32

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

time and do not interfere with one another. A task can be a program (e.g., the Windows Calculator) or an instance of a program (e.g., opening the Windows Calculator multiple times).Multitasking is the apparent simultaneous performance of two or more tasks by a computer's central processing unit.

TIME-SHARING Is an approach to interactive computing in which a single computer is used to provide apparently simultaneous interactive general-purpose computing to multiple users by sharing processor time. Because early mainframe computers were extremely expensive, it was not possible to allow a single user exclusive access to the machine for interactive use. But because computers in interactive use often spend much of their time idly waiting for user input, it was suggested that multiple users could share a machine by using one user's idle time to service other users. Similarly, small slices of time spent waiting for disk, tape, or network input could be granted to other users. Computers capable of providing time-sharing services would usually operate in batch mode overnight. These solutions alone were not sufficient to build a fully functional time-sharing system. In order to provide smooth service to multiple users, a time-sharing system needed a way to deal with multiple processes that did not frequently pause for input/output. This required a hardware interrupt system capable of pausing a running process, and giving processor time to another process.

MEMORY & STORAGE DEVICES

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AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

INTRODUCTION

Memory of a computer deals with storage of information. The secondary storage devices, which retain information in the absence of electrical power, are also discussed.

TYPES OF MEMORY The memory is used for storing information. It is classified into two groups

1)Primary memory 2)Secondary memory PRIMARY MEMORY: Is generally termed as computer’s memory, the main memory. The primary or internal storage is a most essential part of all computers. The internal storage area is made up of several small storage areas called locations or cells. Each of these locations can store a fined number of bits called word length of that particular storage unit. Each location or word has a built in and unique number assigned to it. This number which is used to identify the location is called the address of the location. The primary memory actually functions when the computer operates and is present in the computer in two different forms RAM & ROM.

RANDOM ACCESS MEMORY (RAM): The primary storage is generally referred to as random access memory (RAM) because one can select and use any location of this memory to directly store and retrieve data instructions. Every location of the memory is easily accessed and time taken in each case is same. 34

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

The facility of read/write from a RAM chip entitles it to call read/write memory. When the power is switched off, the information stored in RAM is lost.

READ ONLY MEMORY (ROM): In this memory storage information is permanently stored. The information contained in can only be read and not written fresh information into it. When power is switched off the information stored inside a ROM is not erased, ROM memories are also known as field stores, permanent stores or dead stores.

CACHE MEMORY: A very high speed memory used to increase the speed of processing is employed between CPU and main memory whose access time is close to the processing speed of the CPU. This type of memory is called a high-speed buffer or cache memory. However, cache memory is not addressable by the user of the computer system. Cache memory makes the main memory of the computer appear to be faster and larger than what it really is. The cache memory is normally very small due to its high cost of construction, cache memory improves the memory transfer rate and also increases the processor space.

ACCESSING METHODS OF STORAGE DEVICES The memory of a computer is not actually concentrated in one place, Storage devices are scattered throughout the machine. For instance, the operation registers are flip flop registers which are used in the arithmetic and control units of the computer. 35

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

The storage devices are used to introduce information to the computer from the “ outside world” and to store results from the computer. The procedures for locating information may be divided into two classes: 1. Random access storage devices and 2. Sequential access storage devices. A RANDOM ACCESS STORAGE DEVICES : is one in which any location in the device may be selected at random access to the information stored in direct and approximately equal access time is required for each location. A SEQUENTIAL ACCESS STORAGE DEVICE: is one in which the arrival at the location desired may be preceded by sequencing through other locations, so that access time varies according to location. For example, if we try to read a word stored on a real of magnetic type and the piece of tape on which the word is stored is near the center of the reel, it is necessary to sequence through all the intervening tape before the word can be read. Another way to subdivide storage devices is according to whether they are static or dynamic A static storage: is one in which the information does not change position example flip flop, tape are of static storage devices. A dynamic storage: Devices are devices in which the information stored is continually changing position. Circulating register utilizing change coupled device (CCD) delay lines are example of dynamic storage devices. SEQUENTIALLY ACCESSED DEVICES: Punched paper tape: The paper tapes normally 1 inch (2.54 cms) wide are available in rolls of different length. Data is coded on the paper tape in the form of punched hole combinations, The length of the tape may be kept as required by the user. The information is recorded as holes punched in rows across the width of the tape. Each row represents one character. The maximum numbers of holes per row is known as number of channels on the tape. An eight-channel tape is generally used in computers. A line of sprocket holes in the middle of the tape is provided for the purpose of feeding the tape through the tape punching and reading device. 36

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

Disadvantages i)

Less numbers of characters can only be stored.

ii)

The paper tape media gets easily torn. Advantages

i)

Storage capacity of paper tape is unlimited

ii)

Cost per bit stored is very low

MAGNETIC TAPE: This is most popular storage device for large data that are sequentially accessed and processed magnetic tape is a half-inch (1.27-cm) wide plastic ribbon, which is coated on the side with an iron oxide material which can be magnetized. The tape ribbon is housed in a cassette. The computer tape can be erased and reused indefinitely. The stored data on the tape gets automatically erased as and when fresh data, is recorded in the same area of the tape. RECORDING OF INFORMATION: Information in binary is recorded on the tape as invisible magnetized and non-magnetized spots on the iron oxide side of the tape. 0 of the binary is represented by a non-magnetized spot and 1 is represented by the magnetized spot on the tape. The tape is divided into horizontal rows called channels or tracks and into vertical columns called frames. Each character of the information is recorded per frame based on the code of the computer.

DATA TRANSFER RATE: The product of tape density and tape speed is known as the data transfer rate of the magnetic tape. The number of frames per inch length of the tape is called tape density. The tape density of a magnetic tape is expressed in characters per inch (CPI) or bytes per inch. The tape speed is measured in inches per sec. Data transfer rate of a magnetic tape may even exceed 1 million bytes per second.

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

ADVANTAGES OF MAGNETIC STORAGE:

1. The storage capacity of a magnetic tape is unlimited. 2. It possesses high data density 3. Its cost is much less than other data storage devices 4. Its rate of data transfer is high 5. It is very easy to handle magnetic tapes 6. It is very easy to transfer information from one place to another.

DRAW-BACKS OF MAGNETIC TAPES:

1. As magnetic tape is a sequential access devices, the data recorded on tape cannot be addressed directly. The data item at the end of the tape will require abnormal access time because all the characters before the data item need by processed. This is why magnetic tape device is not found suitable in case data is frequently required to be accessed at random. 2. It is not possible to interpret, the stored data to know the content of the information. 3. Dust free environment is needed for magnetic tapes and the reel containers. a) TAPE CASSETTES: A high quality digital cassette similar in appearance to the home cassettes. b) CARTRIDGES: The large cassette which contains long strips of magnetic tape is called cartridge. It is very convenient to mount the tape there is proper protection against dirt and contamination. Both cassettes and cartridges have low data transfer rate, i,e , less than 10,000 bytes/sec.

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Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

RANDOM ACCESS DEVICES: MAGNETIC DISK:

It is a thin, circular metal coated on both sides with a magnetic material similar to a gramophone record. A number of magnetic disks mounted about half-an-inch apart from each other on a central shaft which may rotate at speed of 2400 or more revolutions per minute (RPM), consists a disk pack. Magnetic disk packs are the most popular medium for direct access secondary storage. Information is stored on both sides of the disks except the upper surface of the top disk and lower surface of the lower disk. Each face of the disk is divided into a number of invisible concentric circles called tracks. A set of corresponding tracks in all the surfaces is called a cylinder. Each track is sub divided into sectors. Information is recorded on the tracks of a disk surface in the form of minute magnetic spots. The magnetized spot represents a 1-bit and non-magnetized spot represents a 0-bit. The information stored on a disk can be read a number of items and reading operation is non-destructive. To write a new data, the previously stored data has to be erased. The storage capacity of a disk pack primarily depends on the number of disks it contains. The storage capacity also depends on the track per inch of surface and the number of bits per inch of track.

MAGNETIC DRUM:

Magnetic drum is also a direct access storage device that can be used for both sequential and random processing. It is basically a cylinder with a magnetizable outer surface. A motor rotates the cylinder on its axis at a rapid speed but constant rate. The surface of the drum is divided onto a number of tracks upon which data is stored as magnetized spots similar to that of a disk. Data is stored on the magnetizable surface of the cylinder as minute magnetized spots arranged in binary form in the series of parallel circular tracks. Recording of data on the rotating drum and reading data from the drum is achieved by a set of secondary read/write heads positioned very

39

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

near to the drum surface. Writing a new data on the drum erases the previously stored data simultaneously at that location. Data once recorded on the drum remains intact until it is erased. The drum rotates at a speed of few hundred to few thousand rotations per minute and its access times are fast. Random access is possible to select any particular track of the drum but once this track is identified, the data is recorded or retrieved sequentially. To reduce the access time, sometime heads are divided into two sets. Heads are positioned diametrically opposite i.e for a drum of 20 track 40 heads is provided. As compared to magnetic disks, data transfer rates are faster. capacity, use of magnetic drum storage is on decline.

Due to limited storage

WINCHESTER DISK:

Winchester disk are also used as a storage device. In this unit, disks are permanently housed and hermetically sealed in contamination free containers. The disks are coated with a special lubricant which minimizes the friction between the read/write heads and the disk surface .Computers using these sealed housings are said to employ Winchester technology. The Winchester technology enables greater precision of alignment, an increase in the number of tracks on the disk surface and a higher storage density per track. Winchester disks are fast and highly valuable and low priced compared with conventional hard disk drives. They are available in sizes varying form 5.25” to 14” in diameter and there capacities are 10,12 and 20 megabytes. Dual disk drive doubles the capacity. Winchester disks are used in large computers.

FLOPPY DISK: A floppy disk is a circular Mylar disk coated and magnetically sensitive film. Since the thickness of the Mylar disk is only a few thousandth of an inch it is named as floppy. The floppy diskette is coated with a magnetic material and enclosed in a protective jacket. The floppy disks are used for backup of files and to transfer files from one computer to another computer Floppy diskettes can be classified as Single and double sided.

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AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

If only one side of the diskette is used to store information such a diskette is called as a single sided disk. If both the side of the diskette is used to store information such a diskette is called as a double-sided disk. The diskette surface is logically divided into a fixed number of tracks (concentric circles). Data can be read and written on the specified tracks and not in between the tracks. Each track is divided into a number of sectors. The number of sectors in a track depends on the size. User’s label Write Protect notch

Manufacturers Labs

Clamping hole Index hole Head slot

Fig 5.1 Floppy Disk A read/write head contacts the disk through the head slot to read from or write to the disk. It is designed such that it can move both forward and backward. The outermost track is numbered as track 0. The subsequent tracks are numbered sequentially. The Index hole is used as a reference point to indicate the beginning of a track. There is a facility to use a diskette only for reading previously stored information and to prevent any attempt to write new information on it through the write protect notch. If this notch is open writing on the diskette is permitted. Advantages of floppy disks are: 

They are very cheap compared with other storage



They greatly enhance the on-line storage capacity



They are also convenient off-line storage medium

 The floppy disks generally available in market are of 3½, 5¼ or 8-inch diameter size. 41

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

APPLICATION OF COMPUTERS IN BUSINESS Corporate computing has revolutionized the business environment with the computer - assistance of many time-consuming, complex tasks such as accounting, inventory control, customer databases, shipping control, and financial analysis. Today’s desktop computers are versatile and relatively inexpensive. They have replaced the typewriter and, in many cases, the personal assistant for wordprocessing and organizational services. Networking of all the company’s desktop computers allows access to and storage of the full range of company resources and information, reducing paperwork and increasing the productive flow of information. The links included herein relate to business and corporate computing.

Marketing is the process by which goods are sold and purchased. The aim of marketing is to acquire, retain, and satisfy customers. Modern marketing has evolved into a complex and diverse field. This field includes a wide variety of special functions such as advertising, mail-order business, public relations, retailing and merchandising, sales, market research, and pricing of goods. Businesses, and particularly the marketing aspect of businesses, rely a great deal on the use of computers. Computers play a significant role in inventory control, processing and handling orders, communication between satellite companies in an organization, design and production of goods, manufacturing, product and market analysis, advertising, producing the company newsletter, and in some cases, complete control of company operations. In today's extremely competitive business environment businesses are searching for ways to improve profitability and to maintain their position in the marketplace. As competition becomes more intense the formula for success becomes more difficult. Two particular things have greatly aided companies in their quests to accomplish these goals. They are the innovative software products and the World Wide Web. More and more manufacturing businesses are integrating some aspects of production, including inventory tracking, scheduling, and marketing. This idea, known as computer-integrated manufacturing (CIM), speeds processing of orders, adds to effective materials management, and creates considerable cost savings. In addition to designing and manufacturing a product, a company must be effectively able to advertise, market, and sell its product. Much of what passes for business is nothing more than making 42

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

Unit- 1st

COMPUTER ORGANISATION

CAM (MBA-1st Sem)

connections with other people. What if you could pass out your business card to thousands, maybe millions of potential clients.

COMPUTER LANGUAGES

MACHINE LANGUAGE

A computer understands information composed of only zeros and ones hence it uses binary digits for its operation. A program written in the form of 0’s and 1’s is called machine language program. There is a specific binary code for each instruction. For eg: to add the contents of register A and register B, the binary code is 10000000 for Intel 8085 microprocessors. The binary code for certain operations differs from computer to computer.

ASSEMBLY LANGUAGE

Writing programs in machine language is very difficult, tiresome and boring job for a programmer, it is error phone. To solve this problem and to facilitate programmer easily understandable languages have been developed. Assembly language is one of them. Programs can easily be written in alphanumeric symbols instead of Zeros & Ones meaningful and easily remarkable symbols are selected for this purpose. Example: ADD, for addition, SUB for subtraction CMP for comparison. Such symbols are called mnemonics. A program written in mnemonics is called assembly language program. ASSEMBLER

A program which translates an assembly language program into a machine language program is called an assembler. 43

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

Assembly language  Assembler  Machine language (Source Program)

(Object program)

Disadvantages 1. Programming is difficult and time consuming 2. The assembly language is machine oriented i.e the programmer must have the knowledge of the hardware of the computer 3. The program written in assembly language for one computer cannot be run on another computer.

HIGH LEVEL LANGUAGES

A High level language is one which is expressed in terms of simple English like language. In computing, a high-level programming language is a programming language with strong abstraction from the details of the computer. In comparison to low-level programming languages, it may use natural language elements, be easier to use, or be more portable across platforms. Such languages hide the details of CPU operations such as memory access models and management of scope. This greater abstraction and hiding of details is generally intended to make the language userfriendly, as it includes concepts from the problem domain instead of those of the machine used. A high level language isolates the execution semantics of computer architecture from the specification of the program, making the process of developing a program simpler and more understandable with respect to a low-level language. The amount of abstraction provided defines how 'high-level' a programming language is. The first high-level programming language to be designed for a computer was Plankalkül, created by Konrad Zuse. However, it was not implemented in his time and his original contributions were isolated from other developments

The instructions written in high level language are called statements. The statements more clearly resemble English Mathematics as compared to mnemonics. Example: BASIC, PASCAL, FORTRAN, COBOL, ALGOL, LISP, ADA, SNOBOL

44

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

Advantages 1. They are easier to learn as compared to assembly languages. 2. They make programs easier and faster to write 3. Provide better documentation. 4. The programmers does not have limitations to use a single type of machine. 5. Programs are portable i.e. they will run on any computer Many high level languages have been developed, some are for general purpose and some for special purposes. Example: PASCAL, PL/1, ADA AND C are general purpose languages. COBOL is for business purposes PROLOG is for logical reasoning BASIC for new comers SNOBOL for text processing SOURCE LANGUAGE AND OBJECT LANGUAGE

The language in which a programmer writes programs is called source language. It may be high-level or assembly language. The language in which the computer works is called object language or machine language. COMPILER

A program which translates high-level languages into a machine language program is called compiler. For example, WATFOR (FORTRAN compiler), TURBO PASCAL compiler. INTERPRETER

An interpreter is a program which translates statements of a high level language program into machine code.

45

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st

CAM (MBA-1st Sem)

In translates one statement of the program at a time. It reads one statement of a high-level language program translates it into machine code and executes it. Then it goes to the next statement. On the other hand a compiler translates the whole program into machine code-

High –level Language

Compiler or Interpreter

(Source Program)

Machine language (Object program)

QUESTION/ ANSWER KEYS State True or False: 1. Machine language is one which is expressed in terms of 0's & 1's. 2. Assembly Language is one which is expressed in terms of mnemonics 3. Compiler is a software which converts machine language to high level Language. 4. Fortran is a low level language. Answers : 1. True

2. True

3. False

4. False.

QUESTION/ ANSWER KEY 1.

A _____________________ is a fast and accurate electronic ( or data)

manipulating system that will accept and store input data, process them and produce output results. 46

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA

COMPUTER ORGANISATION

Unit- 1st 2.

CAM (MBA-1st Sem)

_________________________ are facts or informational raw materials

represented by symbols 3.

Arranging classified data in a predetermined sequence to facilitate processing is

called ______________________. 4.

The word " data" is the plural of datum which means __________________.

Answers: 1. Computer

2. Data 3. Sorting 4. Fact

Mark True or False True

False

1. Electrical or electromechanical components are known as hardware. 2. A Program is considered as hardware 3. Keyboard is considered as output device

Answers: 1. True

2. False

3. False

Prepared By MOHAMMAD DANISH (Lecturer, CSE Deptt.) Al-Falah School of Engineering & Technology, Dhauj, Faridabad

47

Prep. By MOHAMMAD DANISH (Lecturer, CSE Deptt.)

AFSET , MBA