22810845 Fundamental of Computer

8/9/2019 22810845 Fundamental of Computer

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Computer Fundamental By Raju Sharma/1

What is Computer?

Computer is an electronic device. It accepts raw data from us, process it andgives meaningful information as required by user as per given instruction.

Characteristics of a Computer

(a) Computer is very fast.(b) Computer is accurate.(c) They can process millions of instructions per second.(d) Computer is very versatile.(e) Computer works at constant efficiency.(f) Perform repetitive tasks very well without error.(g) Computer can store information for future retrieval or use.(h) Computer can communicate with other computer systems.

History of Computers450 BC - ABACUS

The Egyptians developed it and Improvements made by Chinese & Japanese.

1614 AD - Napier's BonesDeveloped by John Napier Scottish Mathematician. A set of 11 rods further divided

into 9 diagonal numbered parts, based on logarithms. Improved in 1917 AD.

1620 AD - Slide RuleWilliam Oughtred developed it, which is an analog device.

1642 AD - Pascal's Adding MachineBlaise Pascal, a French Philosopher consisted o mechanical gears. It is forerunner

of all mechanical machines.

1694 AD - Gottfried Calculating MachineDeveloped by Gottfried Von Leibnitz, a German Mathematician who was an

improvement over Pascal's adding machine.

All the above were based on mechanical precision and since mechanical precisionwas not that accurate during those days the reliability of the machines was ratherquestionable.

1880 AD - Jacquard Punched Cards MachineJoseph Jacquard, French textile manufacturer, developed a machine, which used

punched cards to make intricate patterns on woven cloth.

Absence of hole = Leading to warp thread raised

Presence of hole = Leading to warp thread not raised

This basic principle of one or other of the two states is the fundamental basis ofthe binary coding system used in computers.

1623 AD - Binary CodesThe first use of binary codes for numerical representation by Francis Bacon.

1822 AD - Difference Engine & Analytical EngineCharles Babbage, English Professor of Mathematics developed both of them. In

Difference Engine the level difference between the values computed for a formula,remains the same.

For example,Compute the Squares of first 6 natural numbers


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Number Square1 12 43 94 165 25

6 36

We compute the level of differences 2 times since we have squared thenumbers and find that the level difference at the 2nd instances are equal as below :-

Squares 1st Difference 2nd Difference1 14 4 - 1 = 3 3 - 1 = 29 9 - 4 = 5 5 - 3 = 2

16 16 - 9 = 7 7 - 5 = 225 25 - 16 = 9 9 - 7 = 236 36 - 25 = 11 11 - 9 = 2

Similarly, if we work out the cubes, the third level difference will be equal. Basedon this principle Charles Babbage developed ANALYTICAL ENGINE which could calculateup to 20 decimals at about 60 additions per minute. However, financial constraints andinadequate technological advancements (electricity was discovered only in 1840's), hisdevices remained unfinished. But for his pioneering work he is called the FATHER OFCOMPUTER.

Similarly, Lady Ada Lovelace is famous as the First Programmer, for havingdevised a suitable use of Binary Number system for programs and data to be fed into theAnalytical Computer.

GEORGE BOOLE developed the application of logic in computers, which whenapplied to mathematical operation came to be known as Boolean Algebra.

1889 AD - Card Punching & Reading MachineHerman Hollerith, a census statistician at the US Census Bureau developed card

punching and reading machines. He formed his own company later, "The ComputingTabulating Recording Company" which is better known today as one of the largestmanufacturers of computers - IBM or International Business Machine Corporation -Headquartered in the USA.1906 AD - Thermionic Valves

Lee De Forest, in 1906, made a breakthrough in developing the technology of"Thermionic Valves".

1937-1944 AD - MARK I Computer

Howard Aiken with IBM's support built the first automatic Electro-mechanicalcomputer using relays and switches.

The BUGSThere is a well known fable about Mark I which indication to the adoption of the

word "BUG" for use in computers.

Once Mark I developed a certain fault and no amount of effort was spared to locate thesame. Every portion of the huge Mark I, computers of those days used to be monstrouslybig machines occupying several rooms, was thoroughly searched for the fault. Afterspending considerable time and effort it was found that on one of the electricalconnections of the "Back-Plane Panel" of the machine a "MOTH" had got struck bringingthe machine to a grinding halt. The moth was removed when Mark-I started functioning.

It was then stated that "Mark I was 'Debugged'."


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Bug was incorporated into the computer vocabulary to mean all kinds of errorsand like-wise debugging meant removing those errors. These two words are commonlyused words now in relation to both the hardware and software of computer.

1946 AD - ENIACElectronic Numerical Integrator and Calculator were developed for World War II

use. After this the progress in the Digital Computers has been simply stupendous(amazing).

JOHN VAN NEUMANNOutlined the basic requirements for the design of modern digital computers.

These relate to the binary coding scheme for data representation, storage of data andprogram within the computer, the manipulation of programs by other programs, choiceof alternative procedures and use of input- output devices for feeding data and retrievinginformation.

Generation of computersFirst Generation -:(1946 - 1954) Use Vacuum Tubes

Use Assemble language for programminglarge in sizeslow processingExample : IBM 704, IBM 709, EDVAC, UNIVAC etc.

Second Generation -:(1955-1964) Use of transistors instead of vacuum tube

Increased Operating speeds & improved Storage devicesHigh speed card readersUsed high-level languages such as FORTRAN (1956),COBOL (1960),Line printers and magnetic tape transport units.Reduction in size, improved reliability, reduction in operating cost.Example : IBM 1400, IBM 7040, CDC 3600, GE635, B300

Third Generation -:(1965-1974) Use of IC (Integrated Circuit)

Starting use of Semiconductor Memory (RAM or ROM)More miniaturization Reliability and AccuracyExample : IBM 370, Honeywell 200, B2000

Fourth Generation -:(1975-up till now) Use of VLSIC (Very Large Scale Integrated Circuit) and

Magnetic Oxide SemiconductorOperating system speed in nano & pico sec.Refinement of I/O units.

Reduction in size.Refinement of HLL and software packages for DBMSReduced operating cost, recording of errors.

Fifth Generation -: (Development continued...)Will be use ULSIC (Ultra Large Scale Integrated Circuit)Use Artificial IntelligenceSuper Computer. This type of computer will understand natural languages like

English, Hindi etc. and programmer have to instruct only what to do, not how to do.These computers will have full ability to understand sounds and visions & it will reducethe burden of programming.


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Classification of ComputerComputer can be classified into four part :-1. MicroComputer -: There are two types of Microcomputer -

(a) Home Computer : Use TV for OutputUse Cassette/floppy as backing storageLow Cost (A few thousand of rupees)

Use for Home education, Home games etc.(b) Business Computer :Use a Separate VDU for output

Floppy or Hard disk for backing storageUsed by Small business and company departmentMore powerful Micros have Mini like Capacitiescalled Super Computer

Types of Business Computer :- PCPC - ATPC - XTPC - AT 286PC - AT 386PC - AT 486Pentium I/II/III/IV

2. Mini Computer -: Multi User, Multi Tasking, Faster than MicroComputer,Larger memory capacity, Larger C.P.U./A.L.U.Cost a few lacks of rupeesNeed site preparation and air conditioned environmentNeed UPS (Uninterrupted Power Supply)

3. Main Frame -: Faster than Mini computerCost a few ten lacks of rupeesUsed by Big companies, banks and government

4. Super Computer -: Have greater processing powerUsed as whether forecastingUsed in Oil exploration, Energy conservation,Nuclear Reactor,Safety Analysis etc.

Application of ComputerToday computer is going to be an essential part of our life. In many part of life, we

can think life without computer. It is useful at so many places among someone are:-(a) Education (b) Library(c) Medical Science (d) Engineering(e) Agriculture (f) Industry(g) Scientific Research (h) Traffic Control(i) Design (j) Checking of Examination Paper

(k) Media (l) Airways & Railways Ticket Reservations

Computer System

Computer System consists of :-a) Hardware - Hardware is the consist of the mechanical, electrical andelectronics part of the Computer.b) Software - Software is the set of detailed step by step instructionscalled program through which user instruct the computer to do something.c) Heartware or Liveware - Heartware is the people who schedule theoperation of hardware and write or modify the software.d) Firmware - Firmware are the routines or programs that are stored inread-only memory (ROM). Unlike RAM, ROM retains programs intact even in the

absence of electrical power. Startup routines and low-level input/outputinstructions are stored in firmware.


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HARDWAREHardware may be classified as :-

1. CPU (Central Processing Unit)2. Peripherals

1.) CPU - CPU may also be classified as :-a) CU (Control Unit) - The CU controls and directs the operations of the entirecomputer system. The control unit retrieves computer instructions in propersequence, interprets each instruction and then directs the other parts of thecomputer system for the execution.b) A.L.U. (Arithmetic & Logic Unit) - The ALU actually carries out Arithmeticoperations like addition, subtraction etc. and Logic operations like comparison ofvalues etc.c) Main Memory - Memory is the mind of the computer. It may be classified as:-i) RAM (Random Access Memory) - It is a temporary memory used for

storing data or instructions during processing. Any storage location can bedirectly accessed using its address. RAM loses its contents when the power isturned off and hence is also known as Volatile Memory. While the computer is on,

information can be written onto the RAM chips and read from them.ii) ROM (Read Only Memory) - It is a permanent memory which contains basicinformation the CPU needs when you first turn on the computer as well as at othertimes during the operation of the computer. This information is written ontothe chip during manufacture. Information can only be read, and no newinformation can be written onto the ROM. There is also some kind of ROM:-

a) PROMb) EPROMc) EEPROM

2. PERIPHERALS :- It can be classified as :-a) Input - Data is accepted as Input through the standard Input device. A numberof storage devices are using now a days as -

* Keyboard* Joystick* Mouse* OCR* MICR* Punch card Reader etc.

b) Output - Processed data is delivered as Output through input/output device. Anumber of output devices are also available as -

* Printer* Plotter* Screen (Monitor) etc.

c) Backing Storage or Secondary Storage - These devices are used to store

the data for a long time permanently. A number of backing storage devices is alsoavailable as -

* Floppy - 31/2" (Capacity - 1.44 MB)

5-1/4" (Capacity - 1.2 MB)

* Harddisk - Capacity from 20 MB to 40 GB and above* Zip drive* CD-ROM* Magnetic Tape* Cartridge Tape etc.


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REPRESENTATION OF INFORMATION :Modern computers are based on Binary system. Binary devices works only on two

stages - "ON" and "OFF". The stages are represented as "0" and "1" which is known as"Binary Digits". Programs and instructions is handle by computer as string of bits.Microcomputer and some other computer as well handle 8 bits at a time.

A set of 8 bits is known as a "Byte".

4 bits or a half of a byte is known as "Nibble".

So,8 Bit = 1 Byte1024 Byte = 1 KB (Kilobyte)1024 KB = 1 MB (Megabyte), i.e. 10,48,576 Bytes.1024 MB = 1 GB (Gigabyte), i.e. 1,07,37,41,824 Bytes.

DATA PROCESSING CONCEPTS :Manipulation of facts to the advantage of the users is called data processing. It

may be done using manual or electronic methods. The main purpose of electronic dataprocessing (EDP) is to do complex jobs at incredible speed and accuracy.

Different cycle in which data is processed electronically is given below :Input Cycle : In this phase, data is prepared in some convenient form and

on a medium most suitable entry into a processing machine.In manual system, we may prefer to write data in a tabularform on a sheet of paper such as the marks sheet ofstudents of a class. We do so, because it is very convenient

to read the marks written in tabular form. In case ofelectronic data processing machines, we may record data ona magnetic tape or floppy disk.

Processing Cycle: In this cycle, we manipulate or combine the inputted datawith other data as per the instructions. In a manualprocessing cycle, a class teacher adds the marks secured byeach student in different subjects. He divides this aggregateby the maximum marks and calculates the percentage ofmarks. He can also award a grade, based on the percentageof marks. In an electronic data processing system theseactions are performed automatically in accordance with aseries of instructions called a program, which is stored in thecomputer. The computer will do exactly the same job as is

told to it by the set of instructions or program.Output Cycle : Once data are processed, the results need to be brought out

in a form most suitable for the user. This is called the outputcycle. In the marks processing case, the marks of eachstudent in each subject are transferred to printed reportcards. Remarks like pass/fail are also recorded on this reportalong with the merit and the grades. A class teacher doesthis job in a manual data processing system and by acomputer printer in an electronic data processing system.


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TYPES OF SOFTWARE

1. SYSTEM SOFTWARE - System Software or System Packages are sets of one ormore programs that are basically designed to control the operation of a computersystem. They are general programs written to assist users in the use of the

computer system by performing tasks, such as controlling all of the operations,moving data into and out of a computer and all the other steps in executing theapplication program. In general, system packages support the following :

(a) Running of other software(b) Communicating with peripheral devices such as printers,card readers, disk and tape devices etc.(c) Development of other types of software.(d) Monitoring the use of various hardware resources such asmemory, peripherals, CPU etc.System software thus makes the operation of the computer systemmore effective and efficient.

2. APPLICATION SOFTWARE - Application software, or Application packages aresets of one or more programs designed to carry out operations for a specified

application. For example, every month a payroll package produces the payslipsfor the workers of a company. Similarly an inventory package may produce thelist of different parts/equipment available in an organization.

Traditionally, application packages are limited to thegeneral-purpose functions of production schedule, general ledgerand general accounting packages. Since there is a great demand ofgeneral-purpose software, therefore there is ever increasingdevelopment of software. Special purpose packages have also beendeveloped for such areas as banking, hospital administration,insurance, desktop publishing, manufacturing etc.

DIFFERENCE BETWEEN SYSTEM AND APPLICATION SOFTWARE :System software offers several advantages and conveniences to application

programmers and computer users. Good systems software allows application packagesto run on the computer with lesser time and effort. Without system software, applicationpackages cannot be run on the computer system. However, the production of systemssoftware is a complex task that requires extensive knowledge and considerablespecialized training in computer science.

Systems programmers, who prepare systems software, are highly trainedcomputer specialists and important members of the computer architecture team.Because of its technical complexity, systems software is rarely developed in-house. Theyare normally developed and distributed by the computer manufacturers. The customerwho buys or leases a computer system would usually receive, in addition to thehardware, some software needed for the effective operation of his computer. A computerwithout some kind of systems software would be very ineffective and most likely

impossible to operate.

OPERATING SYSTEM SOFTWARE - Operating System is a set of programs that isextremely important to activate and Co-Ordinate the activities of various hardwareresources like the processor and input/output devices. In other words, Operating Systemcontrols the movement of information on in the Computer.

OS is the first program loaded into the computer's memory after the computer isswitched on. The operating system is an important component of the computer system,because it sets the standards for application programs that run in it. All programs mustbe written to "talk to" Operating System. The main functions of a OS are :-

(a) It assigns a processors to different tasks being performed by the computersystem.

(b) It allocates the main memory and other storage areas to the system

programs as well as user programs and data.


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(c) It carries out the input/output management and coordinates and assignsdifferent input and output devices while one or more programs are beingexecuted.

(d) It manages files on various storage devices and the transfer of these filesfrom one storage device to another. It also allows all files to be easilychanged and modified through the use of text editors or some other file

manipulation software packages.(e) It establishes and enforces the job priority. That is, it determines and

maintains the order in which jobs are to be executed in the computer system.(f) It automatically transits from job to job as directed by special control

statements.(g) It is able to interpret commands and instructions.(h) It co-ordinates and assigns compilers, assemblers, utility programs, and other

software packages to various users working on the computer system.(i) It establishes data security and integrity. That is, it keeps different programs

and data in such a manner that they do not interfere with each other.Moreover, it also protects data from being destroyed by and other user.

(j) It also produces traces, error messages, and other debugging and errordetecting codes.

(k) It maintains internal time clock and log of system usage for all users.(l) It facilitates easy communication between the computer system and the

computer operator (human).

STORAGE AND RETRIEVAL SOFTWARE - These utility programs facilitate transfer ofdata from one I/O device to another. They make possible the copying of data from oneunit, for instance, magnetic tape to another unit, for instance, magnetic disk. It is alsopossible to copy data from one tape unit to another tape unit or from one disk unit toanother disk unit. This results in a more efficient utilization of the data preparationequipment.

CUSTOM MADE SOFTWARE - Custom made software is the package that is designedand programmed for a particular customer, in contrast with software packages that areavailable off-the-shelf for a particular industry, such as insurance or banking. Softwarepackages, such as spreadsheets and database management systems, although canned,off-the-shelf packages themselves, are designed to create customized solutions to auser's problem as well.

GENERATION OF LANGUAGESThe term "Generation" of computer language is used to categories the generic

enhancements in the various computer languages that have evolved over the last 50years. Each generation indicates significant progress in making computers easier to use.In the early days of computing, it was assumed that only a few elite technical specialistswould learn to use computers, but now their use by a larger proportion of population istaken for granted.

Computer languages by generation are classified as follows :(a) First Generation (Late 1940s) Machine Code.(b) Second Generation (early 1950s) Assembly language(c) Third Generation (Late 1950s

to 1970s) High Level Language(d) Forth Generation (Late 1970s

onwards) including a whole range of structured query languages andother tools.

FORTH GENERATION LANGUAGE (4GL) - Forth generation language is non procedural- that is, the programmer specifies what has to be done, but not how the task is to beperformed. Some 4GLs are aimed at the end user, and ease of use is then a prime

consideration. Professional computer experts design others, which could be described asvery high level languages, for use, and their main objective is to cut down on


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development and maintenance time. Some, such as ORACLE, offer a number of tools(SQL*CALC, SQL*FORMS, SQL*REPORT) suitable for an end user.

Comparison of Third and Fourth Generation Languages

Third Generation Language Forth Generation Language

Meant for use by professional programmers May be used by non-programmingprofessionals (i.e. users) as well asprofessional programmers.

Requires specification of how to perform atask.

Requires specifications of what task toperform (system determines how to performthe task).

All alternatives must be specified. Default alternatives are built-in. User neednot specify these alternatives.

Requires large number of proceduralinstructions.

Requires far fewer instructions (less than onetenth in most cases).

Code may be difficult to read, understand,and maintain by the user.

Code is easy to understand and maintain.

Difficult to debug. Errors are easier to locate because of shorterprograms, more structured code, and use ofdefaults.

Typically file oriented. Typically database oriented.

Q. Explain the difference between assembly language and machinelanguage.

Ans. A computer understands information composed of only zeros and ones. A programwritten in terms of "0s" and "1s" is called a machine language program. Computerinstructions are written binary codes. A machine language uses only binary codes.To write a program in a machine language is a very difficult, tiresome and veryboring job. Moreover, it is errorprone. To overcome this difficulty a program can bewritten in alphanumeric symbols instead of "0s" and "1s". Meaningful symbols

called mnemonics are used for this purpose. For example ADD is used for addition,SUB for subtraction, CMP for comparison etc. A language, which uses mnemonics, iscalled an assembly language program.

When a program is written in a language other than machine language,the computer will not understand this. Therefore, a program written in otherlanguages must be translated into machine language before it is executed. Thetask of translation is done by software.

A program, which translates an assembly language program into amachine language program, is called an Assembler.

Q. Differentiate a high-level language from an assembly language.Ans. A language in which each statement or an instruction is directly translated into a

single machine code is known as a low-level language. Each mnemonic of an

assembly language has a unique machine code. An assembly language is a low-level language. An assembly language depends on the internal architecture of aprocessor. Each processor has its own assembly language. Assembly language ofone processor cannot be used for another processor. In other words it is notportable. To write an assembly language program, a programmer must have thedetailed knowledge of the instruction set of the particular processor, it's internalarchitecture, registers, and connection of peripherals to ports etc. It is not very fastand easy programming language.To overcome the difficulties associated with assembly language, high level or

procedure-oriented languages have been developed. In a high-level language aninstruction is called statement rather than mnemonic. Statements more closelyresemble English and Mathematics than mnemonics. High-level languages permitprogrammers to describe tasks in the forms, which are problem oriented rather

than computer oriented. Programming in a high-level language does not requireprecise knowledge of the architecture of a processor, which is to be used. A


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program written in a high-level language will run on any computer, which has acompiler for that language. In other words a high-level language is portable.

Q. Give the difference between compilers and interpreters.Ans. An Interpreter is a program, which translates statements of a high-level

language program into machine codes i.e. in the form of 1 and 0. It translates one

statement of the program at a time. It reads one statement of a high-levellanguage program translates it into machine code and executes it. Then it readsthe next statement of the program, again translates and executes it. In this way itproceeds further till all the statements of the program are translated and executed.

On the other hand, a compiler goes through the entire high-level languageprogram once or twice and then translates the entire program into machine codes.A compiler is 5 to 25 times faster than an interpreter is. An interpreter is a smallprogram as compared to a compiler. It occupies less memory space, so it can beused in a smaller system, which has limited memory space. The object programproduced by the compiler is permanently saved for future reference. On the otherhand, the object code of the statement produced by an interpreter is not saved. Ifan instruction is used the next time, it must be interpreted once again andtranslated into machine code. For example, during the repetitive processing of the

steps in a loop, each instruction in the loop must be reinterpreted as the loop isexecuted.

Q. Differentiate between system software and application packages?Ans. System software is normally developed and distributed by the computer manufactures. The

customer who buys or leases a computer system would usually receive, in addition to thehardware, some software needed for the effective operation of his computer. Actually asystem software works as a mediator of Computer's hardware and Liveware. It acceptsinstructions from user and controls the hardware of the computer accordingly.

Good system software allows application packages to be run on the computer with lesseffort. Without system software, application packages cannot be run on the computersystem. Application software are those software who may be developed to perform anyspecific task, desired by user, such as for accounting purpose, word processing purpose etc.

Q. Write short notes on Multiprogramming and Time-sharing.Ans. Multiprogramming

In multiprogramming a computer processes several programs simultaneously.Usually a CPU is much faster as compared to I/O devices. While I/O devices areperforming certain tasks the CPU may not be doing any task, i.e. it may be lyingidle. To keep CPU busy for most of the time, it is desirable to process a number ofprograms concurrently. This is achieved by overlapping CPU and I/O operationswhen several programs are running simultaneously.TimesharingUsers enter data at very slow rate, and computer processes data at very fast rate.Making use of this fact a computer serves several users simultaneously byattending them in turn. It usually gives 20-millisecond time to each user. Each userfeels that he is using the computer exclusively because the computer processes hisdata as fast as he enters it. Thus, a timesharing system has many terminals linked

up to the same computer at the same time. In timesharing, the CPU time is dividedamong all the users on a scheduled basis. Each user can utilize the commonresources such as high-speed printer, computer's memory etc.

Q. What is ASCII code? Explain its use?Ans. ASCII is a binary code for data that is used extensively in communications, in most

minicomputers and in all PCs. It stands for American Standard Code for InformationInterchange. ASCII that was originally a 7-bit code allowing 128 possible charactercombinations, the first 32 of which is used for communications and printing controlpurposes. Since today's common unit of storage is an 8-bit byte and ASCII is only 7bits, the extra bit has been as a parity bit or for a variety of different symbols. Forexample, the IBM PC uses the additional 128 characters, called extended ASCII forlines, borders, foreign languages and special graphics symbols.

Q. Explain the term - Hardware, Software, Firmware and Liveware.

Ans. Hardware : All the mechanical, electrical and electronics parts of the computersystem is known as the Hardware of the computers.


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Software : Software is the program who instructs the hardware to perform anyspecific tasks in a certain way.Firmware : Firmware is the programs stored in read-only memory (ROM). Unlikerandom access memory (RAM), read-only memory stays intact even in the absenceof electrical power. Start-up routines (bootstraps programs) and low-levelinput/output instructions are stored in firmware. It falls between software and

hardware in ease of modifications.Liveware : Liveware is the human beings employed to handle hardware andsoftware. It is a slang for computer trained people.

Q. what is Cache Memory?Ans. Cache memory, a small buffer storage, smaller and faster than main storage

(often made of Static RAM), that is used to hold a copy of instructions and data inmain storage that are likely to be needed next by the processor and that have beenobtained automatically from main storage such as hard disk. Cache memory is usedto increase the speed of processing by making current programs and data availableto the CPU at a rapid rate.

A cache is useful when RAM accesses are slow compared with the microprocessorspeed because cache memory is always faster than main RAM memory.

A disk cache is a portion of a computer's RAM set aside for temporally holding

information read from disk. A disk cache does not hold entire files, as does a RAMdisk. Instead, a disk cache is used to hold information that either has recently beenrequested from disk or has previously been written to disk. For example, a programmight need to read in repeatedly from disk either a portion of itself or the sameportions of a data file. If the required information remains in a disk cache, accesstime is considerably faster than if the program must wait for the disk-drivemechanism to fetch the information from disk.

Q. What is Mnemonic?Ans. Any kind of mental trick we use to help us remember. For example, a computer

may be designed to interpret the machine code of 1111 (binary) as the subtractoperation, but it is easier for a human being to remember it is SUB. The SUB isknown as mnemonic code for subtraction.

Q. Give the reason for using binary digits to code data stored in a computer.Ans. A bit is a single digit in a binary number (1 or 0). Within the computer, a bit is

physically a memory cell, a magnetic spot on disk or tape or a pulse of high or lowvoltage travelling through a circuit. Computers, which are in use today, are digitalcomputers. They manipulate numbers. They operate on binary digits 0 and 1. Themain reason for operating on binary digits is that it is much easier for the computerto distinguish 1 or 0 because either the voltage is present or not present. Thus adigital computer operating on the binary digit is more accurate as it can distinguishbetween the presence and the absence of a voltage.

Q. Write short notes on TSR Programs.Ans. TSR (Terminate and Stay Resident) programs are RAM resident programs that

remain in memory at all times whenever a computer is switched on so that they

can be instantly activated. In IBM compatible PCs running under DOS, desktopaccessory TSR programs have become popular in order to have instant access to acalculator or calendar. However, these TSR programs often conflict with each other,each one fighting for the right to exist within the computer, and variouscombinations of programs will not work together. Windows environments for DOSsuch as Windows 3.11 or Windows 98 etc. provide the ability to switch back andforth quickly between multiple applications.

Q. What is Computer? What are the advantages and disadvantages ofcomputer?

Ans. Computer is an electronic device. It accepts raw data as well as instructionsfrom the user, process it and gives meaningful information as required by user as

per given instruction.

Advantages: -


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(a) Computer works very fast.(b) Computer gives accurate result.(c) It can process millions of instructions per second.(d) Computer is very versatile.(e) Computer works at constant efficiency.(f) Perform repetitive tasks very well without error.

(g) Computer can store information for future retrieval or use.(h) Computer can communicate with other computer systems.

Disadvantages: -(a) If wrong programmed then it produces wrong answers.(b) If it gets down then so many working hours wasted.(c) It brings unemployment because one computer can handle work of manypeople.(d) Stealing of information through computer is become too much easy.(e) Computer on Internet is not safe due to Virus or other attacks.

Q. Explain the different component of a computer system? Discuss therespective roles played by the different components of CPU? What is the

role of Input and Output devices in a computer system? Name few ofthem.

Ans. Computer System consist of :-a) Hardware - Hardware is consist of the mechanical, electrical andelectronics part of the Computer.b) Software - Software is the set of detailed step by step instructionscalled program through which user instruct the computer to do something.c) Heartware or Liveware - Heartware is the people who schedule theoperation of hardware and write or modify the software.d) Firmware - Firmware are the routines or programs that are storedin read-only memory (ROM). Unlike RAM, ROM retains programs intact evenin the absence of electrical power. Startup routines and low-levelinput/output instructions are stored in firmware.

HARDWAREHardware may be classified as :-

1. CPU (Central Processing Unit)2. Peripherals

1.) CPU - CPU may also be classified as :-a) CU (Control Unit) - The CU controls and directs the operations of theentire computer system. The control unit retrieves computer instructions inproper sequence, interprets each instruction and then directs the otherparts of the computer system for the execution.b) A.L.U. (Arithmetic & Logic Unit) - The ALU actually carries out

Arithmetic operations like addition, subtraction etc. and Logic operationslike comparison of values etc.c) Main Memory - Memory is the mind of the computer. It may beclassified as:-

i) RAM (Random Access Memory) - It is a temporary memoryused for storing data or instructions during processing. Any storagelocation can be directly accessed using its address. RAM loses itscontents when the power is turned off and hence is also known asVolatile Memory. While the computer is on, information can bewritten onto the RAM chips and read from them.ii) ROM (Read Only Memory) - It is a permanent memory whichcontains basic information the CPU needs when you first turn on thecomputer as well as at other times during the operation of the

computer. This information is written onto the chip duringmanufacture. Information can only be read, and no new information


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can be written onto the ROM. There are also some kind of ROM:-a) PROMb) EPROMc) EEPROM

2. PERIPHERALS :- It can be classified as :-

a) Input - Data is accepted as Input through the Input device. Keyboard isknown as Standard Input Device. Input device makes availability of data toCPU to process it or store it for future retrieval. Without inputting data orinstructions, a computer is not become able to perform any action orprocessing. So minimum one input device is must for every computer. Itmay be like keyboard through which any thing can be fetched or it may belike Optical devices like Scanner, OCR, OMR etc., which can directly capturedata for computer. Pointing devices like mouse, joystick, tracking ball etc.can be used to fetch only instructions to the computer system. A number ofstorage devices are using now a days are -

* Keyboard* Joystick* Tracking Ball

* Mouse* OCR (Optical Character Reader)* OMR (Optical Mark Reader)* OBR (Optical Barcode Reader)* MICR (Magnetic Ink Character Reader)* Punch card Reader* Mike etc.

b) Output - Processed data is delivered as Output through Output device.After processing it is compulsory to get result either in form of soft copy (i.e.on screen) or in form of hard copy (i.e. through printer). These outputs maybe distributed between required persons and authority for their informationpurpose. Later these outputs may use as input for any other processing job.A number of output devices are also available as -

* Printer (Dot Matrix, Ink-Jet, Laser etc.)* Plotter (Used in Engineering purpose)* Screen (VDU-Visual Display Unit, Liquid Crystal Display) etc.

c) Backing Storage or Secondary Storage - These devices are used tostore the data for a long time permanently. A number of Backing storagedevices are also available as -

* Floppy - 31/2" (Capacity - 1.44 MB)

5-1/4" (Capacity - 1.2 MB)

* Harddisk - Capacity from 20 MB to 120 GB and above

* Zip drive* CD-ROM* Magnetic Tape* Cartridge Tape etc.

Q. What are the five basic operations performed by any computer system?Ans. All computer systems perform the following five basic operations: -

1. Inputting - Fetching data as well as instructions in the computer's memory sothat it can be process by the CPU. It may be fetching character one by onethrough keyboard or it may be capturing data through any optical device likescanner, OCR etc.

2. Storing - Inputted data first stored in the computer's memory becausecapacity of the CPU register is not so much that it can receive and process allthe data at a time. CPU receives data and instructions one by one. Theintermediate results should also be remaining in the computer's memory for


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next operation. After all, if we not completed or completed the today's taskthen also it may require in future. So, storing of data and instructiontemporarily or permanently is must.

3. Processing - It is the most vital task of computer system. It can compute thedata as per given instructions in form of programs or software and then givesmeaningful information. As soon as we change the instruction, the output may

differ.4. Outputting - After processing user demands for a result, which is given by

computer in form of output through printer, or on screen.5. Controlling - A computer system have so many additional devices attached

with them to perform various tasks. One major task of a computer system iscontrolling its devices and minimizes the collision between them.

Q. How many types of memory a computer has? Justify the need for eachtype?

orThe ROM contains the essential information and the hard disk contains allrelevant programs. What purpose does the RAM serve?

Ans. A computer system has mainly two types of memory: -1. Main Memory/Primary memory - This type of memory have very few storage

capacity and it contains generally small amount of essential data. This have alsotwo major type, i.e.

a) ROM - Read only memory contains firmware given by the manufacturerof the relevant device. This firmware is very useful whenever we start thecomputer or attach a new device to computer. Due to this firmwarecomputer can easily identify the attached device. It is Non-Volatile Memory.b) RAM - Random Access Memory is a volatile memory. Initially it has noany data when computer system boots up. Sequentially it stores operatingsystem's kernel, application system's data etc. However it is volatile innature, but CPU can access any information from here very quick. Its speedis too much greater than hard disk. During processing, CPU also uses it asintermediate device to keep intermediate results of any process. WithoutRAM there is no any difference between a computer and calculator. When auser work on any file then it first saves in computer's memory and thenafter receiving Save command it transfer the data to hard disk.

2. Secondary Memory/Backing Storage - It is generally Non-volatile in nature,which is used to store data permanently for future uses. It has a large size, so itactually stores all the programs like Operating system, application software etc.During processing if the computer needs more RAM than available, then it works asvirtual RAM, known as Virtual memory. To share information from one to anothercomputer we also need some backing storage device.

Q. What are the main components of a PC system unit? Explain eachcomponent?

Ans. A PC system unit has following components: -1. CPU Cabinet - It stands for Central Processing Unit cabinet. Actually it is a

container in which different components like Processor, RAM chip, Sound card,Mother board, hard disk, floppy drive, CD-ROM etc. are fitted by computerassembler. This box is the most important because it contains most expensiveand useful parts of computer. It has so many output and input ports mostly atback side of it through which we can connect several devices like - printer,keyboard, monitor etc. In front it exists power switch and reset button tostart/restart computer. CD-ROM/Floppy drive can only be accessed from frontside.

2. VDU - Visual Display Unit is also known as standard output device. Thisproduces soft copy of entered data and processed results. A user can interactthrough VDU mostly. Major component of VDU is CRT (Cathode Rays Tube).Another type of VDU used LCD (Liquid Crystal Display) which consumes too lesspower and generally used with Mobile computer like Laptop, Palmtop etc.

What type of keys, other than alphabetic and digits, are available


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on a keyboard and for what purpose? How is a key pressed on thekeyboard interpreted by the computer?

3. Keyboard - This is also known as standard Input device. It contains about 104-105 keys in case of a standard keyboard. It has rich set of keys which can beclassified into five major category: -a) Alphanumeric keys - This section contains characters from a to z and 0 to

9 including standard keys available at normal typewriter keyboard.b) Numeric Key pad - This section exists at right side of keyboard, which is

useful, if someone wants to feed only numerical data. This section containsnumbers along with major mathematical operators.

c) Function Keys - These keys are labeled from "F1" to "F12" and performdifferent functions in different languages and packages. Generally thesekeys contain shortcut commands.

d) Cursor Movement Keys - Eight keys including four arrow keys and Home,End, Page Up, and Page Down, exist between alphanumeric and numericsection are known as Cursor movement keys. These keys controls themovement of cursor (A dash like sign who indicates that where we areperforming writing or deleting operation).

e) Special Keys - Esc, backspace, Return, Control, and Alert etc. is known as

special keys. These keys are used to supply some instructions to computersystem either alone or with combination of any other alphanumeric keys.The functions of these keys are vary from application to application.

Any key pressed on the keyboard, actually completes some circuitsexists beneath the keys. These circuits send some binary values tocomputer's input module. From the input module, control unit receivesthese binary values, check and decide whether it has to show on screen (incase of alphanumeric keys) or has to perform some operation (in case offunction or special keys). After decision it prints the character or saves it orprocess in any other manner.

4. Printer - This peripheral device is used to take hard copy of the report. If wewant to keep copy for future use then we must take print out through printer.There are mainly three types of printer: -a) Dot Matrix Printer - An Impact printer who uses 9 or 24 pin to hammer on

a ribbon so that the character or picture appears at another side of ribbonon paper.

b) Inkjet Printer - This printer uses one or two ink cartridge, first one containsblack ink and another contains three colours (Red, Green, and Blue).Combination of these colours produces millions of colours. This is a Non-Impact printer, which generally prints one line at a time.

c) Laser Printer - This Non-Impact printer uses Toner to print on paper. Ituses Laser light to print. Printing quality of laser printer is Superior thanother printers. Its main uses are at Printing press and offices where required

fine and heavy printing.5. UPS/CVT - Uninterrupted Power Supply/ Constant Voltage Transformer is usedto supply required level of electric supply to all computer components. Thecomputer components are very sensitive in term of electric supply, so it needsconstant voltage. Some operating system or application software also need toclose it in proper way (Shut Down), so, we must keep UPS in case of such an OSor Application Software.

Q. Write short notes on ASCII?Ans. ASCII is a binary code for data that is used extensively in communications, in most

minicomputers and in all PCs. It stands for American Standard Code for InformationInterchange. ASCII that was originally a 7-bit code allowing 128 possible charactercombinations, the first 32 of which is used for communications and printing controlpurposes. Since today's common unit of storage is an 8-bit byte and ASCII is only 7

bits, the extra bit has been as a parity bit or for a variety of different symbols. Forexample, the IBM PC uses the additional 128 characters, called extended ASCII for


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lines, borders, foreign languages and special graphics symbols.Q. Errors occur in computer due to human rather than technological

weaknesses. Discuss.or

Explain "Garbage in Garbage Out".Ans. A machine can work only as per their mechanism created by human being.

Computer has inherited the same thing. We know that computer is consist of somany hardware parts who works as per given instruction through programdeveloped by a programmer. But it is possible that there may be lack of any optionin a circuit to process any specific type of signal. If a programmer wants to processsuch signals it may produce error, but it is not of computer's, it is human beingweakness.

It is also possible that a programmer have limited knowledge about thedeveloping program. For example a computer programmer have if no moreknowledge of Civil or other engineering requirements then he can't develop anyCAD/CAM software for that engineers. If he develop something then it is possiblethat it have not more options or those engineers may reject it. But in this case,again computer is not responsible for that error. Here programmer is responsible.

At last we can say that computer have no any their own capacity of

thinking. It thinks only its programmer thinks. So, it can't work beyond itsprogrammer mind and may be unusable for some users.

Q. What is the difference between a graphical printer and a plotter?Compare in terms of speed, accuracy or quality of output.

Ans. A graphical printer is a printer, which is used to print any type of graphics orphotographs through it. It may be any Dot Matrix, Inkjet or Laser printer. It may becolor or mono. Generally this type of printer prints forward direction only, i.e. thepaper skips forward continuously and the printer's head moves left and right toprint the required text or graphics. So, it is compulsory for CPU to feed theinstructions in the manner that printer need not roll back the paper. To do so, it isimportant that the printing matter should be converted into any image finally atcomputer system and then the printing should starts.

But in case of plotter, it may be one or more pens who are free to move leftto right as well as top to bottom and vice versa. So, the CPU need not create theimage in advance before printing. In the case of Plotter the CPU may fetch bottomside's instruction first and then instructions for topside. It is useful in designingdress materials, map for buildings etc.


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NETWORKING CONCEPTSNetworking is a form of computer communications generally used for the transferof data and information within an organization. Networking in this context refersto the confines of an office, a group of offices, a building or a closely spaced groupof two or more PCs connected together by some type communication media (wireor cable) to form a data path between the computers. Once the PCs are physically

connected, software designed specifically for network. This software also allowsany user to access shared data storage and output devices connected to thenetwork. Examples of shared devices are printers, plotters, imaging devices, harddisks and tape drives.

Need and Advantages of Networkinga. To share Computer Filesb. To share Computer Equipmentc. To enable unlike computer Equipment to communicated. To Improve Communication speed and accuracye. Low Cost of Transfer of Dataf. Instantaneous Availability of Informationg. Multimedia Transfer

LAN (Local Area Network)Local Area networking is a form of computer communications generally used for

the internal transfer of data and information within an organization. "Internal" in thiscontext refers to the confines of an office, a group of offices, a building or a closelyspaced group of two or more PCs connected together by some type of communicationsmedia to form a data path between the computers.

Advantages DisadvantagesEconomic

Shared peripherals such as printers

Technological flexibility

Incremental growth

Less computer memory available

High Cost

Greater complexity

Less user control

Prone to Security lossOrganizational

Improved communications

Improved standardization

Better control

Controlled Security

Data sharing

WAN (Wide Area Network)

Wide Area Network is a network that spans large geographical distances. WANsusually operate at lower speed than LANs. Wide area network (WAN) is a network thatspans large geographical distances. WANs usually operate at lower speed than LANs.

WANs are typically created using specially conditioned telephone lines,microwaves, or satellite data transmission.

NETWORK TOPOLOGY Topology is the way networks are physically connected together. Topology

determines the complexity and therefore the cost of network cables installation.Topology also determines the strategy for physically expanding the network. There isseveral type of topology but mainly three type are :-1. STAR TOPOLOGY - Each node is connected to a single, centrally located file

server, using its own dedicated segment of cable. This topology has the

advantage of minimum data traffic along the cables (node to server only), thusproviding optimum performance. But because a single machine must co-ordinate


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all the data communications, this requires an extremely powerful and expensivefile server.

2. RING OR CIRCULAR TOPOLOGY - In this layout, each node is physicallyconnected to only two others. Each node passes information along to the next,until it arrives at its intended destination. Performance is faster on this systembecause each portion of the cabling system is handling only the data flow

between two machines.3. LINEAR BUS TOPOLOGY - In this layout, a single main cable connects each

node, in what amounts to a single line of computers accessing it from end to end.Each node is connected to two others except the machines at either end of thecable, which are connected only to one other node. The network operating systemkeeps track of a unique electronic address for each node and manages the flow ofdata based on this addressing scheme.

4. TREE TOPOLOGY- This is a network topology containing zero or more nodes thatare linked together in a hierarchical fashion. The topmost node is called the root.The root may have zero or more child nodes, connected by edges (links); the rootis the parent node to its children. Each node can in turn have zero or morechildren of its own. Nodes sharing the same parents are called siblings. Everynode is a tree has exactly one parent node (except for the root, which has none)

and all nodes in the tree are descendants of the node. These relationships ensurethat there is always one and only one path from one node to any other node inthe tree.

5. GRAPH TOPOLOGY- In this method of connection, zero or more nodes are linkedtogether in an arbitrary fashion. Any two nodes in a graph may (or may not) beconnected by a link. Not all the nodes in a graph need to be connected, but if apath can be traced between any two nodes, the graph is a connected one.

COMPUTER VIRUS

Q. What is Computer Virus?Ans. A Computer virus is a small block of coded instruction that obtains control of a

PC's CPU and directs it to perform unusual and often destructive actions. Virusknows how to copy itself and attaches itself to other programs, which furtherspread the infection.

Anti-Virus is the method to get rid of perverse software or the viruses.

There are following types of viruses :-

(a) TROJANS HORSE - A Trojans Horse is a program that invades a computer systemby secretly attaching itself to a valid program downloaded into the computer. Itmay be used to locate password information or it may alter an existing program tomake it easier to gain access to it.

(b) Time and Logic Bombs - A time and logic bomb is a program that destroys data;

for example it may reformat the Harddisk or randomly insert garbage into datafiles.A time bomb formats the Harddisk on a given date or slows down computer every

Friday.

(c) Melissa and SKA virus - Melissa virus attacks MS-WORD or MS-EXCEL files andspread very fast. This virus changes the Normal.Doc, disabling the macroprotection message and inflects all the Word files opened or created subsequently.

Sometimes Melissa virus spread around the world rapidly infecting manycomputers and bringing down networks.

SKA increases the size of the file and change the extension of the files to .SKA.These virus delete the Microsoft Document files or change their contents.

Virus Scanner and Remover - Virus scanners are products designed to help identifyviruses within files, boot sectors, master boot sector, memory and other hiding


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places, name them and eventually remove them. The capability to detect andidentify a virus is probably the most important feature of a scanner.

In most cases scanner comes with remover. Remover detects the quality of virusand removes it.

Vaccine Program is a program that watches for typical things that virusesdo, halts them and warns the computer operator about the computer security being

threatened.

INTERNET

INTRODUCTION The Internet is a loose connection of thousands and thousands of computer

networks scattered all over the globe. The only thing all the networks have in common isthe use of the same transmission language, known as TCP/IP. However, you need notknow anything about TCP/IP to use the Internet.

The Internet started as a US government project in the 1960s called theARPANET (Advanced Research Projects Agency Network) which was initially Network ofSecurity Department of US. At its initial period scientists and engineers used it only. Aftermore government and educational institutions got involved, it grew into an internetwork.

Since 1993, the internet has been a hot topic - with more and more people getting to useit at a current rate of about a million new connections a month all over the month.

WORLD WIDE WEBThe World Wide Web is one of the most popular parts of the Internet. The Web is

made up of hypertext documents stored on servers around the world. Hypertextdocuments contain links you can click on to move to another section of the page, todifferent documents, or to another type of Internet resource, such as electronic mail (e-mail) or newsgroups.

Web pages include text, graphics, animation, sound and sometimes movies also.The rich content, along with the ability to jump from one page to other page using links,has contributed to the explosive growth of the Web.

BROWSERThese are a software who organizes the information of the Internet and then

systematically produce it to you. Netscape Navigator was the first popular browser butnow-a-days Internet Explorer has been using widely.

INTERNET SERVICE PROVIDER (ISP)ISPs means a company who provides Internet Services. This type of company

takes some charges from user and then provides services for some time. ISP gives ausername and password to users with some local telephone numbers. First of all userdials to ISP with any one of these local telephone numbers and then after askingusername and password, company connects the user with Internet.

UNIVERSAL (UNIFORM) RESOURCE LOCATER (URL)Many companies keep their data and information on World Wide Web. So, addressof these companies should be unique. URL is the unique name of that company. It hastwo parts - First one indicates about the protocol and second one denotes IP address ofthat company. For example in http://www.microsoft.com, http (HyperText TransferProtocol) is the protocol and microsoft.com is the IP address.

HOMEPAGEHomepage is the main page of any Web Site. Generally a Homepage have all

possible links of that Web Site. It may be understood as Contents of that Web Site.

SURFINGSurfing means without any planning wandering on different Web-sites to either

search any type of information or answer of any question.


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SEARCH ENGINEThis is an utility provided by different portal to search any information on World

Wide Web. After giving some word in search dialog box and requesting for search, thesearch engine searches and returns a list and links of similar Web Sites containing givenwords. After it user can search his information on that sites.

INSTANT MESSANGER Through the Internet and suitable software if someone talks with any other

person, then this talking is known as CHATTING. Generally chatting has been donethrough Host site, where user select desired room and then desired person for chatting.But in this system there is a problem that a user has to choose any person from a longlist of known or unknown persons.

But through the Instant Messenger a user creates list of those persons from whomhe wants to chat. After it when any person among that list become online, indicatorshows that person's name through blinking or through any sound etc. Through thisInstant Messenger a user can talk to their limited persons.

DOWNLOAD & UPLOADTo copy any information from World Wide Web or any other computer located far

away, is known as Downloading. For this purpose either File Transfer Protocol (FTP) orHypertext Transfer Protocol (http).

Uploading is just reverse of Downloading. In Uploading a file may be copy toServer from the current computer.

E-MAILFull form of e-mail is Electronic Mail. In this system a user has a unique name.

This name can be hire from any ISP or some Portal provides free facility to create an e-mail address through that portal. After gaining an e-mail address user can send anyletter in electronic form to someone other or can receive any mail, which was sent by anyother person to him.

ATTACHMENTAdditional data, which will be send through e-mail, is known as Attachment. This

attachment may be any text, audio, video or photo file.

DOMAIN NAMESMost organizations use domain names that are easy to remember. Each domain

name ends with an identifier that tells what type of web site it is. Following is thecommonly used identifiers :

Current Domain Identifiers.com Commercial business.edu Educational institutions.gov Government entities

.net Internet Service Providers.mil Military Sites

.org Organizations that do not fit any other categoryProposed Domain Identifiers

.arts Cultural and entertainment-related organizations

.firm Business

.info Information services

.nom Web sites of individuals

.rec Recreation-related organizations

.store Stores and shops

.web World Wide Web-related organizations.

INTERNET EXPLORER

Internet Explorer is a browser developed by Microsoft Corporation and a freeware.When we open it then following items come on the screen :-


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Title Bar - On the left the title bar displays the name of the web page currentlyopen and on the right side the maximize/minimize, restore and close button.Menu Bar - It is located just below the title bar, same as other application.Toolbars - It is located just below the Menu bar and generally it has followingbuttons :-

Back- Displays a page in the list of previously viewed

pages.Forward - Displays a page in the list next to viewed pages.Stop - Stops downloading the current page.Refresh - Downloads the current page again, ensuring that the

latest version of the web page is displayed.Home - Displays the home page.Search (Toggle) - Displays (or hides) the Search Explorer Bar in left

pane, which provides access to Internet SearchEngines.(Default through MSN search).

Favorites - Displays (or hides) the Favorites Explorer Bar in leftpane Which provides access to our favorite sites.Using Favorites commands, we can create a list offavorite pages and organize them into folders. Then

to go to a favorite page we simply select the page wewant from the Favorites menu.

To add the Web pages to our Favorites listeither we have to choose Add to Favorites fromFavorite menu or click Add to Favorites on theFavorites Explorer Bar at left pane. In the comingdialog box, Type the name of the page against theName and then select the location of the favoritepage through Create In box. We can also use drag ordrop feature to add any pages to Favorites.

If we choose Organize Favoritesoption from Favorites menu then we can easily view,organize and return to favorite page as much assimilar to Windows Explorer.

History (Toggle) - Displays (or hides) the History Explorer Bar at leftpane that provides access to sites we have visitedrecently.

Full Screen (Tgl)- Switches to (or from) full screen view, which providesmaximum viewing space for Internet Explorer'sdocument area.

Mail - Launches your mail or newsreader program(by default - Outlook Express) and lets you send linksand pages to others via e-mail.

Print - Prints the current page, if the printer is online.

22810845 Fundamental of Computer

Documents