DOS(DISK OPERATING SYSTEM)

 DOS

    The full name of dos is Disk operating system. This is the most popular disk operating system which is applied in Micro computer. Dos developed by Tim Pitterson 1981 named 86-Dos.
Then in July 1981, Microsoft purchased all right to 86-dos, made substantial alternations to it, Ms. Dos as its primary operating system was released in the year 1981. (Named Ms. Dos 1.0)
When Micro Computer with hard disk was developed in 1983, Ms. Dos 2.0 came in to the market. In 1984, Ms. Dos 3.0 and Ms. Dos 4.0 version were developed.
            The latest version of Ms. Dos is Ms. Dos 7.1.

Booting
Loading of in to main memory involves of their essential files of dos such as IO. Sys, MS-DOS. Sys, Command.Com in to the main memory. Loading these files in to main memory is called booting.

Booting Process                                              

                         On

                          ↓

                       RAM

                          ↓

                    BIOS [Basic Input-Output System]

                          ↓

                      POST [Power on Self Test]

                          ↓

        Loads dos on to the memory

                          ↓

                  Dos Prompt

When you switch on the computer. First the BIOS present in its permanent memory tests all the devices. This process is called POST (Power on Self Test) after that the operating system present on the disk is stored in the Dos memory (RAM) and with it the main files of Ms. Dos are executed these files are-

• IO. Sys
• Command.Com
• Ms-Dos. Sys
• Autoexec.Bat
• Config. Sys
• HIMEM. Sys etc

In the end Ms. Dos Prompt is display on the computer screen.

The Dos Prompt
Having loaded the Dos in Ram in the disk, it displays a prompt on the screen, which tells that the system is ready to take instructions from you. This prompt is a way to use the efficiency of Dos. You type your command on this prompt. This command prompt is display in the following way
C:\>_
C:         -           Name of Current Drive
\           -           Name of current Directory
>          -           End of the Prompt
_          -           Cursor

File name in Dos
To decide the file name of file, these are the following rules-
[I]        There can be two parts of a file name-
(a)        Primary Name
            It can be given in maximum 8 characters. Such as Sales, Purchase etc.
(b)        Extension
It maximum, can be fixed 3 characters.
(II)       Dot (.) is used between, primary file name and extension.
(III)      No blank space can be given between the letters of the computer file name.
(IV)      File name of two are more files cannot be similar.
(V)       The command of Ms. Dos can’t be used as file name.
(VI)      Special symbol can’t be used as file names, such as -, [,  ] , /, <,  > etc. 

Dos Commands
Dos commands are two types- 

(1) Internal command

(2) External command

Internal Command
These commands are always available with dos because these commands are automatically stored in the memory at time of booting. All these commands are collected in command.Com program file. Internal commands are DIR, REN,VER etc.

External Command
Eternal command are such short program which are stored either on floppy disk or hard disk and if need be, they are executed and stored in the memory. External Commands are-PROMPT, CHKDSK, EDIT etc.
 
Internal commands of Dos

VER                This command displays the version number of Ms. Dos you are working open.
Syntax-            C :\> VER

VOL                This command displays the volume label and serial number.
Syntax-            C :\> VOL
DATE              This command displays the current data and enables you to reset it
Syntax-            C :\> DATE

TIME              This command display the current time or reset it. 
Syntax-            C :\> TIME
Syntax-            C :\> TIME

CLS                 When you want to clear the screen and get command prompt to the                               first line on screen.
Syntax-            C :\> CLS

COPY CON    This command is used to create file in Dos.
Syntax- C:\> Copy Con <File name>
Example- C:\> Copy Con NIST
After typing the matter we save the file press Ctrl +Z key combination or F6 function key. 

TYPE              This command displays the contents of any file.
Syntax-            C:\> Type <File name>
Example-         C:\> Type NIST

REN                This command is used to change the name of any file.
Syntax- C:\> REN <Old file name> <New file name>

Example-C:\> REN NIST NIST2

COPY             This command is used to make the duplicate copy of any file.

Syntax-            C:\> Copy <Source file name> <Target file name>
Example-C:\> Copy NIST NIST4
Syntax-            C:\> COPY <Path of source file name> <Path of target file name>
Example-C:\> Copy C:\> NIST D:\ NIST5

­

DEL                This command is used to delete the specified file.
Syntax-            C:\> Del <File name>
Example-         C:\> Del NIST

PROMPT        This command changes the Ms. Dos command prompt.
Syntax-            C :\> PROMPT <Prompt Name> or <$Character>
Valid characters for prompt command are given below-
Characters                              Value they give
$q                                                        =
$$                                                        $
$T                                                        Current system time
$D                                                       Current system date   
$P                                                        Current working directory (e.g. - C:\>
$G                                                       >
$L                                                        <
$V                                                       Version number
$N                                                       Default drive
$B                                                        !
Example-

(1)        C:\> Prompt NIST                    Output-            NIST_
(2)        C :\> Prompt $P$G                   Output-            C:\>

CHANGING THE DRIVE
The computer pays attention to only on drive at time. If you want your computer to work in another drive type the name of the drive and the color after it-
Example-         C:\>D:              Output- D:\>

DIR                 This command displays the lists names of all the files and subdirectories under the current working directory. In directory display the following information-

• Dir also lists the drive volume label and volume serial no.
• Display the files and directory name.
• Display files and directory creation date and creation time.
• Display size of files in byte.
• Display number of files and directories in the list.
• Display total space in byte occupied by the files.

Syntax-            C :\> DIR

DIR Command with different switches
We can add switches the list in different ways. The dir commands with switches are as follows-

DIR/P             All the files and directory in the root directory will be display page wise.
DIR/W           All the files and directories the root directories will be display width wise.
DIR/S             Lists the directories with their sub-directories & files.
DIR/L             Display the files & directories name lists in lower case.
DIR/A             Display all types of files (hidden system read-only & normal) in directory listing.
DIR/B             Display the files and directory name list only.
DIR/Y             Display the files & directory listing creation date year in four digits.
DIR/ON         Display the lists directories & file in alphabetical order (A to Z).
DIR/O-N       Display the list directories & file in a reverse alphabetically order largest size.
DIR/OS          Display the files and directories listing by smallest to largest size.
DIR/O-S         Display the files and directories listing by largest to smallest. 
DIR/OD          Display the files & directories listing by oldest to newest date.
DIR/O-D         Display the files and directories listing by newest to oldest date.
DIR/AH           Display the list of hidden file.
DIR/AS            Display the list of system file.
DIR/AR            Display the list of read only files.
 
Wild Card Characters
Two special characters “?”(Question Mark) & “*”(asterisk)  are called will cards in dos similar groups of files are to be copied or deleted this wild cards can be used.

What is question mark (?) Wild Card?
Question wild card is used to introduce one character in the file name. If you want to name a list of those files in (drive) which has 6 characters and their extension name is.EXE. Type the following command-       
C :\> Dir ?????? . Exe

What is Asterisk wild card?
Asterisk wild card is use to display a group of letters in the file name. Support you want to make a list of those files which have their extension name. Exes you will have to type the following command-         
C :\> Dir *.EXE

MKDIRor MD            This command is used to create subdirectories on a disk.
Syntax-C:\> MD <Directory Name>
Example-C:\> MD NIST

CHDIR or CDThis command changes your working directory to the directory you specify.
Syntax-            C:\> CD <Directory Name>
Example-         C:\> CD NIST
CD..                 Makes the parent directory of working directory.
CD\                  Makes the root directory as the current working directory.
RD                   This command is used to remove the directory.
Syntax- C:\> RD <Directory name>
Example-C:\> RD NIST
 
External Command of Dos
EDIT               This command is used to edit the already create file by using copy con command and create a new file.
Syntax-            C:\> EDIT <File name>
Example-         C:\> Edit NIST

LABEL           This command is used to change the disk volume label name.
Syntax- C:\> LABEL

MORE            This command is used to display the long file contents in page wise.
Syntax-            C:\>More <File Name>
Example-C:\>More NIST

MEM               This command displays the current of used and frees memory on your computer.
Syntax-            C:\>MEM

CHKDSK        This command is used to get information about blank space in the disk and memory. It is also used to correct the disorder in the data structure.
Syntax-            C:\> CHKDSK

ATTRIB          This command is used to attribute some features like using this command you can make file hidden or set in to read only form.
Syntax-C:\> ATTRIB <Switch> <file name>
Some switches are as follows-
                        +H       -           Make hidden file
                         -H       -           To turn the file back in to normal mode.
                         +R       -           To set the file in to read only mode.
                         -R       -           To turn the file back in to normal from.
TREE              This command graphically displays the path of each directory and subdirectory on the give drive.
Syntax-[1.]C:\> TREE
[To view the name and paths of all directories and subdirectories on you system.]
[2.]       C:\> TREE/F
[To view file name along with the Directory/ Subdirectory name.]

BATCH FILE A Batch file is used for combining in to one command. When you type the Batch file without the       .BAT extension, the commands in the Batch file are executed. You can create a batch file using any text editor or using Copy Con command.
Syntax-            C:\>Edit <File name>.BAT                   

Or                     C:\>Copy Con <File name>.BAT
 
Autoexec.Bat  Autoexec.Bat is a special batch file that executed automatically when you power up the system or reset it. It can also be executed from Dos by typing Autoexec.

Syntax-            C:\>Copy Con Autoexec.Bat  

 Or                    C:\>Edit Autoexec.Bat

OPERATING SYSTEM

 Operating System

What is Operating System?
Operating system is a controlling Program of the computer. The operating controls the Computer. A Computer cannot communicate with you itself. It needs a medium for it and that medium is the operating system. Thus an operating System is a set or collection of some Programs.
Thus we can say that the operating system controls all the devices of a Computer. The operating system is also called Master control Program.

Types of Operating System

• Single user System
• Multi Programming
• Multi Processing
• Batch Processing

Single user System
A single user operating System is that which executes one program at a time. Earlier, most operating system was single user and even in almost all the modern micro computers are also single user systems.
            The problem with this system is that it is not possible to activate more than one program at a time. It’s why the programs are arranged in a line in this system.

Multi Programming
Now-a-days so many operating systems give the facility to performing several tasks at a time. This is called multi Programming. In others words, the execution of two or more than two programs by one Computer at a time is called multi programming.

Multi Processing   
The use of the word multi processing is to clarify the processing view where two or more processors are linked to each other. In such systems the commands of different and independent programs are controlled by a single processor at a time or the execution of different commands is done one by one by the processors which have been received from a single program.
            Thus we can say that multiprocessing is used in two computers attached to each other which  have more than two CPU’s  and which have the capacity to execution different programs at a time.

Batch Processing

This is a very old method which can execute various programs and is used to execute the task on various data processing centers. In such operating system very user prepares his programs offline and deposits it on data processing center when completed and the computer operator collects all such. Programs the batch of programs, he load it in the computer and the execute them one, by one, batch processing is also called serial, sequential, offline and stacked job processing.

WHAT IS VIRUS?

WHAT IS VIRUS?

Virus

A computer virus unreal is a tiny program with when enters computers, get associated with pre- installed programs and applications and induces malfunction of the affected programs. A computer virus ( a program) when enter the computer districts the proper working of a computer set can after working of a computer in the followings ways- 

• By destroying important in the computer
• By making change in directories
• By formatting floppy or hard disk
• By diminutive the speed o computer processing.
• By altering the function of the key on key board.
• Altering the data store in programs and kills.
• By shaping or hindering the execution of files.
• Flashing irrelevant massage on screen.
• Videoing the booting of a computer.
• By altering the size and structure of files.

When a virus affected program in executed the virus executed itself in the primary memory of the computer.
How a Virus Spreads

• Using a pirated software
• Though a network system
• Though secondary storage device

Types of Computer Virus

1. Boot sector virus                     
2. File virus                                  
3. Polymorphic virus 
4. Partition table virus
5. Stealth virus
6. Macro virus     

Virus Name

• Michelangelo
• Dishwasher
• Trojans
• Bombs
• Worms
• Email-hoaxes

Antivirus Program
Most of the antivirus packages come along with a prevention program that is comp able of defecting the virus before the system become in faceted. The most popular antivirus programs are following-

• Norton antivirus
• Quick heal
• Kasper sky
• Avast
  
  
  

HARDWARE & SOFTWARE

HARDWARE & SOFTWARE
 

HARDWARE

All the electronic & electrical compounds user to construct a computer are rebreeds as hardware. This include device like the keyboard, monitor unit etc.

SOFTWARE

Set of instruction given to the computer to device the hardware. The tern software refers a computer program developed by computer manufacturer or user. Software specified in to their major classes-

• System software
• Application software
• Utility software

System Software

System software is general turn refreshing to any computer software with managers and controls the hardware so that application software can perform a task. It is essential part of computer system. System software is a set of programs that organize, utilize and control hardware in a computer system. System software is following-

• Operating system
• Language processor

Application Software

Application software is those program developed by user and to perform some specific task. Application software includes word processing, Spread sheet, Presentation package, Database Management System, Graphics etc.

Utility Software

Utility software is a type of computer software. It is specifically designed to help manage and turn the computer hardware are there are various utility software you night vase come across. They include disk defragmenter, Virus, Scanners and often PC tools etc.

ANATOMY OF COMPUTER-IV

 ANATOMY OF COMPUTER-IV

STORAGE DEVICE

Storage device is one of three part of computer. There are two types of storage on a computer namely Primary and Secondary. Primary storage of volatile and non volatile. Volatile memory holds data for temporary either electricity goes are computer gets restarted somehow all data get lost. Non volatile primary storage helps start your computer. This contains some very useful firmware to boot with computer. Booting is the process of starting computer. Actually this type of storage is called main memory. Secondary memory is what we used to hold our data for a long period.  Secondary storage comes in different forms. Floppy disk, Hard disk and optical disk are a few to name.

Primary Storage

Memory is a working storage of computer. This is very important part of computer where data, information and programs are kept during processing and are retrieved if needed. Memory is also called primary memory are main memory. Memory uses some spaces for storage that is definite in number called capacity or size of memory.
Computer primary memory is mainly of two types-
 1.   RAM    [Random Access Memory]
 2.   ROM    [Read Only Memory]

RAM

Random access memory is the same as main memory is volatile, means the contents of the memory disappear once the current is turned off. Ram is found in different size 4MB, 8MB, 16MB, 32MB, 64MB, 128MB, 256MB, 512MB and 1GB etc.
Several types of Ram used in Personal Computer-

• Dynamic RAM                [DRAM]
• Synchronous DRAM     [SDRAM]
• Static RAM                      [SRAM]

ROM

Read only memory is a permanent memory of computer. Programs are built into Ram at the factory label and cannot be changed by the user, we can read them, but not alter. ROM is non volatile the contents do not disappear when the current is turned off. Rom is of the following types-

• PROM                 [Programmable Read Only Memory]                                      
• EPROM              [Erasable Programmable Read Only Memory]                        
• EEPROM           [Electrical Erasable Programmable Read Only Memory]        

Secondary Storage

Secondary storage also called auxiliary storage is found physically outside the processor. This is a long term non volatile memory. Though Rom is also non- volatile memory to which data cannot be added. Besides storing data, secondary storage is also use full for transferring them from one computer to another. There are a number of s. storage devices. They can broadly be classified into Magnetic tape, Magnetic Disk and Optical disk.

Magnetic Tape

Magnetic tape is non-volatile storage medium consisting of a magnetic contain on a thin plastic of strip. Nearly all recording tapes are of this type, whether used for video, audio storage or general digital data storage using a computer.

Magnetic Disk

Magnetic disk is another form of sequential access storage, but it is for better for direct for direct access storage. A magnetic disk can be of two forms-

1. Hard Disk
2. Floppy Disk

Hard disk

Hard disk is a non-value storage device which store digitally encode data on rapidly rotating plot here with magnetic surf case hard disk ware originally developed for use with computer. Today, applications for hard disk have expanded beyond computers to in clued digital video recorders, digital audio players, and digital camera and video game consoles. Mobile phones from Samsung and nailed can be found with HDDS.

Floppy Disk

Floppy disks are mode of Magnetic Oxide coated flexible tape material. It is enclosed in a rectangle plastic jacket. Floppy disks are the following two type-
1. Mini floppy                
2. Micro floppy

Optical disk

In optical disk is a flat, usually polycarbonate disk whereon data is stored in the form of pits within a flat surface. This data is generally accessed when a special material on the disk (often aluminum) is illuminated with a laser diode. These pits distort the replanted laser light.
Optical disk are compact disk following.

• CD       [Compact Disk]
• DVD    [Digital Versatile Disk]
• BD       [ Blu -Ray disk]

ANATOMY OF COMPUTER-III

ANTOMY OF COMPUTER-III

OUTPUT DEVICE

The output unit contains many devices used to receive the result obtained by the processing and present it in the human readable form.
Output devices mainly produced two types-    1.  Soft copy output
                                                                                   2.  Hard copy output
Output devices are following-

1.                  Monitor
2.                  Printer
3.                  Speaker
4.                  Earphone
5.                  Projectors

Monitor

Monitor is an output device, we can get our output on a TV like screen, it is commonly classified as- Monochrome, Gray-scale, and color.

• Monochrome is designed, from “Mono” which means “single” and “Chrome” means “color” which means single color monochrome monitor are single color monitor like a black and white TV.
• Gray-scale monitors are special types of monochrome monitors for displaying output in different gray shades.
• Color monitors can give output as a combination of RGB [Red, Green, and Blue] radiations. If a computer has sufficient memory a color monitor can present variety of colors ranging from 16 to 1, 60, 000, 00 colors.

CRT Monitors

Most monitors are based on “Picture tube elements” like a television set. This tube is known as “Cathode Ray Tube”. CRT technology is cheaper and capable of presenting high quality colored outputs.

Flat-Panel Monitors

Recently a new technology in display devices has been developed. In this technology charged chemical gases adopt various chemical configurations to create images on the screen these are called flat-panel display. This device is light in weight and consumes comparatively less electricity. This device is mainly used in laptop computers.
Flat-panel monitor also have LCD technology which means Liquid Crystal Display.
The two more technology in flat-panel display is Gas plasma display [GPD] and Electro Luminescent Display or ELD. Both of these technologies GPD and ELD have better and high quality resolution but these are costlier too.

Printer

Printer is an output device, which prints the output on the paper. The output on the paper in printed form is called “HARD COPY”. The digital signal sent from computer are converted to natural languages like Hindi, English etc. and then printed on paper by printer so that human being can understand.
            Printer can be classified on the basis of variety but on the basis of printing technology, they are mainly categorized in two classes-

1. Impact Printer
2. Non Impact Printer

Impact Printer

This printer type resembles with the printing by a type writer. In this type of printer, a metallic hammer or a print head strikes on paper and ribbon to print characters. For examples- Dot matrix, Daisy wheel, Chain printer etc.

Non Impact Printer

In this type printing method there is no direct striking between print head and paper. For Examples- Inkjet printer, laser jet printer etc.

ANATOMY OF COMPUTER-II

ANATOMY OF COMPUTER-II 

PROCESSING DEVICE
CPU [Central Processing Unit] is the unit of computer system which controls the execution of instruction. This is the most important part of computer. CPU is called brain of computer. The central processing unit performs the following functions-

• It store data and instruction received from the input unit
• It controls the operation of different unit as issue the command to all part of computer system.
• It carries out the data processing.
• It directs the result to the output unit.

The control processing unit consists of the following three parts-

1. CU                      [Control Unit]
2. ALU                   [Arithmetic and Logical Unit]
3. MMU                  [Main Memory Unit]

 
Control Unit
Control unit control the internal process of a computer. It controls the input and output process of the computer. The operation controlled by control unit is as follows-

• It gives commands to the input device to transfer data to the memory and also direct the output to be transferred to the output devices.
• It control the transfer of the data from the memory to the arithmetic logic unit for computation, it direct transfer of calculated data back to the main memory.
• It controls the peripheral device and directs them to do the work as and when required.

Arithmetic and Logic Unit
The arithmetic and logic unit are capable to perform addition subtraction, multiplication and division as well as logical operation. The function of ALU is as follows-

• It carries out the arithmetical operation.
• It performs logical operation like taking division based is conditional computing.

Main Memory Unit
The main memory units are storage section of computer is used to store the information that will be used during the computation. The memory section of computer is also used to help any type of data such as- picture, data, video etc.

ANATOMY OF COMPUTER-I

 ANATOMY OF COMPUTER-I

INPUT DEVICE
An input unit is a device which accepts instructions and data from the user and communicates these to central processing unit of the computer.
In brief the following function are performed by input unit-

• It accepts data and information from the user.
• It converts these instructions and data into computer acceptable form.
• It passes the converted instruction and data to the central processing unit.

Input device are following-

1. Keyboard
2. Mouse
3. Scanner
4. Joystick
5. Light pen
6. Camera
7. Microphone

Keyboard 
Keyboards are designed for the input of text and characters and also to control the operating of a computer.
We can classify the keys of keyboard in six type of understand anatomy as-

• The alphanumeric key             [A to Z, 0-9, Special Symbol]
• The numeric keypad                 [0-9]
• The function keys                      [F1-F12]
• Special purpose keys                [Sleep, Power, Volume etc]
• Modifier keys                             [Shift, Alt, Ctrl]
• Movement keys                         [Up, Down, Left and Right]

Mouse
Mouse is an online input device which can be used by single hand. By moving a mouse on a plane surface.

   Mouse has two or more buttons. Left hand side button is most in use while right hand side button is used in special cases sufficing special purpose. A mouse is generally used to navigate pointer on the screen and to draw pictures and graphics.

Scanner

Scanner is the input device which input data on the paper in the graphics, picture or texts directly into the computer.

OCR, OMR, MICR are the examples of scanner only. Now-a-days variety scanners are available for personal computers with resolutions starting form 300DPI [Dot per inch]. Resolutions refer to the clarity of scanned picture.  The no of dots in a unit area in a picture is called resolution.

Joystick

Joystick is an input device generally used for playing video game.

Light pen

Light pen is used draw any picture or graphics on the computer screen.

A light pen consists of a light sensitive pen like device to select object on a display screen. Any graphic drawn using light pen can be saved into computer and even can be modified and resized.

Camera

Camera is an input device which can store any photograph and movie. After storing camera connect in computer, photo ı are movie transfer in computer.

Bar code reader

Bar code reader is one of the used to read bar code written on the packet of the products. Bar code contains price and other product related information.

ATM [Automatic Teller Machine]

ATM’s are wonderful devices usually come across on the bank campuses, snooping malls, railway stations, airports, bus stands, and public places. These are actually specialized from the input devices for transactions processing.