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MR. SEDNEY BARAZA OJIAMBO, Lecture notes of Computer Science

NOTES FOR COMPUTER PACKAGES AND INTRODUCTION TO COMPUTER SCIENCE

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ACHARYA N.G.RANGA AGRICULTURAL UNIVERSITY
LECTURE NOTES
Course No : STCA-301
Introduction to Computer Applications
Prepared by
P. Sumathi
M.Sc, M.Phil
Assistant professor
Department of Statistics & Mathematics
S. V. Agricultural College
Tirupati
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ACHARYA N.G.RANGA AGRICULTURAL UNIVERSITY

LECTURE NOTES

Course No : STCA- 301

Introduction to Computer Applications

Prepared by

P. Sumathi

M.Sc, M.Phil

Assistant professor

Department of Statistics & Mathematics

S. V. Agricultural College

Tirupati

LECTURE OUTLINE

Course No. STCA-301 Credits: 2 (1+1) Course Title: Introduction to Computer Applications THEORY S. No. Topic/Lesson 1 Introduction to Computers, Definition, Advantages & Limitations 2 Anatomy of Computers – Components of Computers and its functions - Overview of Input devices of Computer 3 Overview of Output devices of Computer, Memory, Processors, Hardware, Software & Speed 4 Types of Software – Operating System, Translators & Programming languages 5 Types of Software – Application Programmes, Utility Programmes & General Purpose Programmes, Classification of Computers 6 Operating System – Functions of OS – Types of OS-DOS and WINDOWS, Booting process 7 Some fundamental DOS commands – FORMAT, DIR, COPY, PATH, LABEL, VOL, MD, CD, DEL and TREE 8 WINDOWS:GUI, Desktop and its elements, Anatomy of a window – Title Bar, Minimize, Maximize, Restore and Close Buttons, Scroll Bars, Menus and Tool - Starting and shutting down of windows 9 WINDOWS Explorer , working with organization of files and folders, Copy, Move and Print files – setting time and date 10 MSWORD: Word processing and units of document, features of word- processing packages 11 MSWORD: Creating, Editing, Formatting and Saving a document in MSWORD – Features of File, Edit and Format menus 12 MSEXCEL: Electronic Spreadsheets – concept, packages, creating, editing and saving a spreadsheet with MSEXCEL 13 MSEXCEL: Use of in-built Statistical and other functions and writing expressions, Creating Data Analysis option in Tools Menu, Use of Data Analysis Tools – Correlation and Regression, t-test for two samples, Creating Graphs 14 MSACCESS: Concept of Database, Units of database 15 MSACCESS: creating database 16 Internet - World Wide Web (WWW), Concepts

INTRODUCTION

Definition : A Computer is an electronic device that can perform activities that involve Mathematical, Logical and graphical manipulations. Generally, the term is used to describe a collection of devices that function together as a system. It performs the following three operations in sequence.

  1. It receives data & instructions from the input device.
  2. Processes the data as per instructions.
  3. Provides the result (output) in a desired form. Data : It is the collection of raw facts, figures & symbols. Ex : Names of students and their marks in different subjects listed in random order. Information : It is the data that is processed & presented in an organized manner. Ex : When the names of students are arranged in alphabetical order, total and average marks are calculated & presented in a tabular form, it is information. Program : Set of instructions that enables a computer to perform a given task. Advantages of computers :
  4. High speed : Computers have the ability to perform routine tasks at a greater speed than human beings. They can perform millions of calculations in seconds.
  5. Accuracy : Computers are used to perform tasks in a way that ensures accuracy.
  6. Storage : Computers can store large amount of information. Any item of data or any instruction stored in the memory can be retrieved by the computer at lightning speeds.
  7. Automation : Computers can be instructed to perform complex tasks automatically ( which increases the productivity).
  8. Diligence : Computers can perform the same task repeatedly & with the same accuracy without getting tired.
  9. Versatility : Computers are flexible to perform both simple and complex tasks.
  10. Cost effectiveness : Computers reduce the amount of paper work and human effort, thereby reducing costs. Limitations of computers :
  11. Computers need clear & complete instructions to perform a task accurately. If the instructions are not clear & complete, the computer will not produce the required result.
  12. Computers cannot think.
  13. Computers cannot learn by experience. Generations of computers : Generation Component used First Generation (1946-1954 )

Vacuum tubes

Second Generation (1955-1965)

Transistors

Third Generation (1968-1975 )

Integrated Circuits ( IC )

Fourth Generation ( 1976-1980)

Very Large Scale Integrated Circuits ( VLSI) Fifth Generation (1980 – till today )

Ultra Scale Integrated Circuits ( ULSI) Micro Processor ( SILICON CHIP)


ANATOMY OF COMPUTERS The computer system consists of three units:

  1. Input device 2. Central Processing Unit (CPU) 3. Output device

Block diagram of a Computer :

The various functions of these units can be summarized as:

Unit Function 1.Input device : Reads information from input media and enters to the computer in a coded form

2.CPU

(a) Memory unit : Stores program and data (b) Arithmetic Logic unit : Performs arithmetic and logical functions (c) Control Unit : Interprets program instructions and controls the input and output devices

  1. Output device : decodes information and presents it to the user

Central Processing Unit : It is the part of the computer that carries out the instructions of a computer program. It is the unit that reads and executes program instructions. Hence it is known as the ―brain‖ of the computer. The CPU consists of storage or memory unit, Arithmetic Logic Unit (ALU) and control unit.

(a). Memory Unit: It is also known as the primary storage or main memory. It stores data, program instructions, internal results and final output temporarily before it is sent to an appropriate output device. It consists of thousands of cells called ―storage locations‖. These cells activate with ―off-on‖ or binary digits(0,1) mechanism. Thus a character either a letter or numerical digit is stored as a string of (0,1) Binary digits ( BITS). These bits are used to store instructions and data by their combinations.

(b) Arithmetic and Logical Unit(ALU): It is the unit where all Arithmetic operations (addition, subtraction etc.) and logical functions such as true or false, male or female are performed. Once data are fed into the main memory from input devices, they are held and transferred as needed to ALU where processing takes place. No process occurs in primary storage. Intermediate generated results in ALU

CENTRAL PROCESSING UNIT

INPUT DEVICE OUT PUT DEVICE

Memory unit

Control Unit

ALU

Input Devices Devices used to provide data and instructions to the computer are called Input devices. Some important input devices are Key board, Mouse, Scanner, MICR, Web camera, Microphone etc.

  1. Keyboard : The Key board is used for typing text into the computer. It is also known as standard Input device. A computer keyboard is similar to that of a type writer with additional keys. The most commonly available computer keyboard has 104 keys. There are different types of keys on the keyboard. The keys are categorized as :  Alphanumeric keys , including letters & numbers.  Punctuation keys, such as colon (:), semicolon (;) Question mark (?), Single & double quotes (‗,‖)  Special keys such as arrow keys, control keys, function keys (F1 to F12), HOME, END etc.

2.. Mouse: It is a device that controls the movement of the cursor on a monitor. A mouse will have 2 buttons on its top. The left button is the most frequently used button. There will be a wheel between the left and right buttons. This wheel enables us to smoothly scroll through screens of information. As we move the mouse, the pointer on the monitor moves in the same direction. Optical mouse is another advanced pointing device that uses a light emitting component instead of the mouse ball. Mouse cannot be used for entering the data. It is only useful to select the options on the screen.

  1. Scanner : : It is an input device that can read text or illustrations printed on paper and translate into digital form. The main advantage of these scanners is that the data need not be entered separately resulting in saving lot of time.

Scanners are of two types: i) optical scanners ii) MICR i) Optical scanners: a. Optical character Recognition(OCR): In this, characters are read with the help of a light. This is used in office atomization, documentation in library etc. b. Optical mark recognition(OMR): It is a technology where an OMR device senses the presence or absence of a mark such as a pencil mark. OMR is used in tests such as aptitude tests. c. Optical barcode recognition(OBCR): Barcode readers are photoelectric scanners that read the bar codes or vertical zebra striped marks printed on product containers. This is used in super markets, book shops etc. ii. MICR: This is widely used in banks to process the cheques. This allows the computer to recognize characters printed using magnetic ink.

  1. Magnetic Ink Character Recognition(MICR): : It is a character recognition technology used primarily by the banking industry to facilitate the processing of the cheques. MICR characters ( cheque No., Acc.No.etc) are printed in special ink usually containing iron oxide. When a document that contains the ink needs to be read, it passes through a machine which magnetizes the ink and there will be a reader sorter unit which translates the magnetic information into characters. MICR provides a secure, high speed of scanning and processing information. It scans about 2600 cheques/min.

Output devices

Any device that is capable of representing information on a computer is called an Output device. Output devices receive information from the CPU and present it to the user in the desired form.

Some important Output devices are : Monitor, Printer

  1. Terminal/Monitor : It is similar to TV screen- either a monochrome (black & white) or colour – and it displays the output. It is also referred as Visual Display Unit(VDU). Several types of monitors are in use. Some of them are Colour Graphic Adapter(CGA), Enhanced Graphics Adaptor(EGA) , Video Graphics Adapter (VGA) and Super Video Graphics Adapter (SVGA). The screen sizes differ from system to system. The standard size is 24 lines by 80 characters. Most systems have provision for scrolling which helps in moving the text vertically or horizontally on the screen.

2. Printer : A printer is used to transfer data from a computer onto paper. The paper copy obtained from a printer is often referred as ―printout‖. The different printers and their speeds are as follows: S. No. Type Mode of Printing Speed 1 Dot – Matrix printer

Prints the character in dotted pattern through printer ribbon using either 24 pin or 9 pin

200/300 to 700 CPS

2 Ink Jet printer Work by spraying ionized ink Slow, 90 CPS 3 Laser printer Also called page printer. Uses laser beam to produce an image.

6 to 12 PPM

4 Line printer Prints lines at a time instead of single characters.

300 to 600 LPM

5 Plotter Produces drawings or graphs through pens which are filled with different colours. ( CPS: Characters Per Second; PPM: Pages Per Minutes; LPM : Lines Per Minute)

Laser printer


ROM :

It is called Read-only memory as information can only be read from and not written or changed onto ROM. ROM is the ‗built-in‘ memory of a computer. It stores some basic input – output instructions put by the manufacturer to operate the computer. The storage of data and instructions in ROM is permanent. It does not depend on the power supply. i.e it is non-volatile memory.

Secondary memory: The primary memory which is faster (and hence expensive) is generally not sufficient for large storage of data. As a result, additional memory, called the ―auxiliary‖ or ―secondary memory‖ is used. It is also referred as ―backup storage‖ as it is used to store large volume of data on a permanent basis which can be transferred to the primary memory whenever required for processing. Data are stored in secondary storage in the same binary codes as in the main (primary memory) storage. Some of the devices of secondary storages are Floppy Disk, Hard Disk, CD-ROM, DVD and Flash drive.

1_._ Floppy Disk : It is also referred as ―Diskette: and is made of flexible Vinyl material. It has a small hole on one side called ―Right protect notch‖, Which protects accidental writing/deleting the information from the disk. There is a hole in the centre through which the spindle of drive unit rotates the disk. The disks are available in two sizes of 5.25 and 3.5 inches and these could be either low- density or high-density floppies. Storage capacity of floppies are measured in kilobytes (KB) and megabytes (MB). The details about the storage capacities of the floppies are presented below: Floppy Disk Storage Capacity Size (Diameter) Low Density 360 KB 5.25 inches High Density 1.2 MB 5.25 inches High Density 1.44 MB 3.5 inches Extended 2.8 MB 3.5 inches

  1. Hard Disk : The hard disk can hold more information than the floppy disk and the retrieval of information from hard disk is faster when compared to floppies or tapes. A hard disk is fixed inside the CPU and its capacity ranges from 20 MB onwards. The hard disk is made up of a collection of discs (one below the other) known as platters on which the data is recorded. These platters are coated with magnetic material. It is less sensitive to external environmental disorders and hence the storage in hard disk is safe. A small hard disk might be as much as 25 times larger than a floppy disk. Storage Capacity of hard disks varies from 20 MB to several Gega bytes like 80GB, 160GB.
  1. CD-ROM : CD-ROM stands for Compact Disk–Read Only Memory. It is used to store a wide variety of information. Its main advantage is that it is portable and can hold a large amount of data.. The storage capacity of most CD-ROMs is approximately 650 MB or 700 MB. CD -ROMs have the following variations: (i) CD-R(Compact disc Recordable): Data can be written onto it just once. The stored data can be read. Data once written onto it cannot be erased. (ii) CD-RW(Compact disc Rewritable): It is also called erasable CD. Data once written onto it can be erased to write or record new information many times. To use a CD-ROM, a device called CD drive is needed.
  2. DVD : DVD stands for Digital Versatile Disc. It is similar to a CD-ROM, except that it can store larger amounts of data. The storage capacity of a DVD is at least 4.7MB. DVDs that can store up to 17GBs are also available. Because of their capacity, DVDs are generally used to store a very large multimedia presentations and movies that combine high quality sound and graphics. 5. Flash Drive : It is a small, portable device that can be used to store, access and transfer data. Due to its small size, it is commonly called Pen drive. It is also called USB drive. We can read, write, copy, delete, and move data from computer to pen drive or pen drive to computer. It comes in various storage capacities of 2GB, 4GB, 8GB etc. It is popular because it is easy to use and small enough to be carried in a pocket. This device is plugged into the USB port of the computer and the computer automatically detects this device.

translates or executes the first instruction before it goes to the second, while a compiler translates the whole program before execution.

The major difference between compiler and interpreter is

  1. Error correction is very much simpler in the case of interpreter as it translates the statements in stages. The compiler produces an error list of the entire program at the end.
  2. Interpreter takes more time for the execution of the program compared to compilers as it translates one statement at a time Programming Languages : There are three types of programming languages.
  3. Machine Languages: Computers respond only to machine language. This language is in terms of binary codes (0,1). i.e. all programs should be written with these codes, which is difficult, time consuming and leading to errors while writing the programs. There is no unique standard machine language. Rather there are many machine languages. These are machine dependent. These are referred as the first generation languages.
  4. Assembly Languages : It uses mnemonic codes rather than numeric codes (as in machine languages). Ex. Add or A is used as a symbol for addition. It requires translators to convert into machine language. Like machine language, writing program in assembly language is also time consuming. These are also machine dependent.
  5. High Level Languages (HLL): These are referred as problem oriented languages (POL). These are referred as third generation languages. The advantages of these languages are

 The high level languages are convenient for writing programs as they can be written without any codes. These languages follow rules like ―English‖ language.  Because of their English like nature, less time is required to write a program.

 They are machine independent. A program written in any HLL can be run on computers of different types without any modifications.

Several High Level Languages which are in common use:

FORTRAN : FORmula TRANslation

COBOL : Common Business Oriented Language

BASIC : Beginner‘s All purpose Symbolic Instruction Code

PROLOG: PROgramming in LOGic

ALGOL : ALGOrithmic Language

  1. Utility Programs: These are pre-written programs supplied by the manufacturer for maintaining day to day activities of computer system.

Example: COPY, SORT, MAILING, virus scanning software etc.,

  1. Application Programs: These are user written programs to do a specific job which can be changed to meet the individual needs. These programs are written in different languages such as BASIC or C or by using database packages like dBASE, Oracle.

Example: Payroll, Billing, Railway Reservation etc.

5. General Purpose Packages: These packages are developed to suit the needs of research workers / scientists in different fields. These packages are categorized as :

i) Data Analysis ii) Word Processing iii) Spread Sheet iv) Graphics and v) Databases

Data Analysis Ex: SPSS (Statistical Package for Social Science), MSTAT, MICROSTAT, GENSTAT, SAS etc. Word Processing Ex: WORD PERFECT, WORDSTAR, MS-Word, CHIRATOR, NORTON EDITOR etc.

Spread Sheet Ex: LOTUS, Qpro, VP-PLANNER, SYMPHONY, MS-Excel etc. Graphics Ex: LOTUS, STORY-BOARD, POWER-POINT etc. Databases Ex: dBASE, FOX-BASE, FOX-PRO, ORACLE, MS-Access etc.

Functions of Operating System : Today most operating systems perform the following important functions :

  1. Processor management : It manages the assignment of processor to different tasks being performed by the computer system.
  2. Memory management : It manages the allocation of main memory and other storage areas to the system programmes as well as user programmes and data.
  3. Input / Output management : It manages the co-ordination and assignment of different Input and Output devices while one or more programmes are executed.
  4. File management : It allows all files to be easily changed and modified through the use of text editors or some other file manipulation routines.
  5. Establishment and enforcement of a priority system : It determines and maintains the order in which jobs are to be executed in the computer system.
  6. Interpretation of commands and instructions.
  7. Facilitates easy communication between the computer system and the computer operator.

d) Micro Computers : A micro computer is the smallest general purpose processing system. Micro computers are also referred as ―personal computers‖(PC). These are self contained units and usually developed for use by one person at a time but can be linked to very large systems. They are cheap, easy to use even at homes and can be read for variety of applications from small to medium range. These are available in three models:

  1. PC : Personal Computer
  2. PC-XT : PC with Extended Technology
  3. PC-AT : PC with Advanced Technology

PERSONAL COMPUTERS Personal Computer: A personal computer has a Monitor (VDU), a keyboard , Disk Drive (s), printer and CPU. The CPU of PC has a mother board with several chips mounted on a circuit board. The major components of the circuit board are : Microprocessor, RAM and ROM chips and other supporting circuits.

Microprocessor: The Microprocessor chip is like a brain of human being which contains circuits and registers to perform arithmetic, logic and control functions. i.e it contains ALU & CU. These chips will be able to retrieve data from the input output devices, store, manipulate and process a byte of data at a time. There is an address bus which is built into these chips to determine the storage locations (of RAM) of the data and the instructions of the program.

Over the years, different microprocessors were developed and the first in the series is INTEL

  1. The other procesors are 8088, 80286, 80386, 80486, Pentium I, II, III and Pentium 4. The Pentium 4 can execute any piece of code that ran on the original 8088, but it does it about 5000 times faster.

Clock Speed : The speed with which the instruction is executed or number of pulses per second is called the clock speed. It is measured in terms of million pulses per second (MHZs).

The following table gives the differences among the different processors that intel has introduced over the years :

S.No. Microprocessor Date Transistors Clock speed Data width 1 8080 1974 6000 2MHZ 8 bits 2 8088 1979 29,000 5 MHZ 16 bits 8 - bit bus 3 80286 1982 134,000 6 MHZ 16 bits 4 80386 1985 275,000 16 MHZ 32 bits 5 80486 1989 1,200,000 25 MHZ 32 bits 6 Pentium I 1993 3,100,000 60 MHZ 32 bits 64 - bit bus 7 Pentium II 1997 7,500,000 233 MHZ 32 bits 64 - bit bus 8 Pentium III 1999 9,500,000 450 MHZ 32 bits 64 - bit bus 9 Pentium 4 2000 42,000,000 1.5 GHZ 32 bits 64 - bit bus 10 Pentium 4 ―Prescott‖

2004 125,000,000 3.6 GHZ 32 bits 64 - bit bus

Peripherals : The input, output and secondary storage units like floppy drives, keyboard, mouse, etc., are called peripherals. Classification of PCs : PCs are mainly classified on the basis of primary memory (RAM), Microprocessor, clock speed and peripherals. The classification is presented in the following table: S.No. PC-Type RAM Microprocessor Clock speed Peripherals 1 PC 640 KB 8088/8086 8 MHZ Floppy Drives, key board and printer 2 PC-XT 1 MB 8088/8086 18 MHZ Floppy Drives, Hard- Disk Drive, Key board and printer 3 PC-AT 1 MB to 32 MB

80286 to 80486 25 MHZ and above

Floppy drives, Hard disk, Keyboard, Mouse and Printer

MS-DOS

MS-DOS is a collection of programs and other files. It is a single user and single programming environment. MS-DOS is designed to provide a method of organizing and using the information stored on disks, application programs, system programs and the computer itself.

Files and File names : A file is a collection of related information. The files should have suitable names for their identification in later use. Rules for naming the files:

  1. File names should be of one to eight characters in length with an option of one to three character extension
  2. File names can include any one of the following characters: A to Z (or a to z) 0 to 9, $, &, #, @. %, ( ), { } The characters which are not allowed are: :, ; + / \ * as these have special meaning
  3. A period (.) is used to separate the first part of a file name from the extension. (LETTER.TXT, RAMA.WK1, etc.,)
  4. When a file name includes an extension, it should be referred along with its extension and not only with the first part
  5. Reserved devices names are not allowed. (COMMAND.COM, DATE, etc., Types of files in DOS : - There are different types of files you can create in your computer, according to the usage. To differentiate each file, the computer will give an extension to identify the different types of files you have created.

Executable Files: The files with extension of either .COM or .EXE are called executable files. These files are directly executed by typing their names (without the extension) by the computer. A file with .COM extension refers to COMMAND file name and the other with .EXE extension refers EXECUTABLE program file. Batch Files: the file containing a series of DOS commands, which are executed automatically one at a time in the order entered, is known as the batch file. A batch file has the extension .BAT. If the batch file is given a special name AUTOEXEC.BAT, it is automatically executed when the computer is switched on or during booting.

Backup Files: These are backup files of a file and have extension .BAK. These files are such that their contents can not be altered (edited). These files are created while working with WORDSTAR package for typing a document. System Files: These are program files developed for system control. They have .SYS extension. Directory: It is a collection of files, size, date and time of creation of files. The relation between files, directories and disk is similar to the relation between papers, filing folders and filling cabinets. Just as a cabinet contain papers and other folders, a directory may contain directories also. The main directory of a drive is called Root Directory into which several directories and sub-directories may exist.

Types of DOS commands : There are two types of commands: i) internal and ii) external i) Internal DOS commands: Internal commands are those commands which manage files. They are loaded into the memory of the PC when PC is booted. These are stored in a large file with file name COMMAND.COM, when a PC is booted.

  1. DIR : Dir displays continuously the directory of file names, file size, date and time of creation. C:>dir a: This command displays the list of files and directories from the drive A i.e. the floppy drive. It can be specified with two options: i ) Dir/p : It pauses the listing of the directory whenever the screen is full. The next screen load of files can be displayed by pressing any key. ii) Dir/w : displays the files of the directory in a five column format. Only file names and their extensions will be displayed without the date and time of creation. The total number of files and remaining bytes are listed. In addition, DIR can also be specified with wildcard characters (such as * or ?) to list files sharing a common element in the file name or extension. Eg: DIR STATS.* : lists all files with STATS and other combinations along with the extensions. DIR *.COM : lists all files with extension .COM
  2. DEL : Deletes a specified file. Syntax: DEL {filename}

Del stats deletes the file ―stats‖. Del stats.* deletes all extensions of the file ―stats‖. Suppose you want to delete a file COMPUTER.DOC on A drive, the command will be: C:> DEL A: COMPUTER.DOC 

  1. COPY: The COPY command is used to copy files from one place to another. The way to execute copy command is to type COPY leave a space followed by the source file name again a space followed by destination file. Syntax: copy {Drive name} {Drive name}

Ex: 1. COPY STATS MATHS copies a file ―STATS‖ with the name ―MATHS‖ on the same drive

  1. COPY PATH A:ENTO copies a file ―PATH‖ from the current drive to drive ―A‖ with the file name ―ENTO‖.
  2. COPY A:MATHS C:STATS copies a file ―MATHS‖ form drive ―A‖ to drive ―C‖ with the file name ―STATS‖
  3. COPY A:MATHS.* C:STATS.* copies all extensions of file ―MATHS‖ form drive A to drive C with name ―STATS‖.
  4. REN : The REN command is used to rename the old file with another name. The way to execute Rename command is to type REN leave a space followed by the old file name again followed by a space and new file name. Ex: Suppose if you want to change the name of a file MATHS.TXT to STATS.TXT the following command will work: C:> REN MATHS.TXT RESULT.TXT