Parts of a computer : The parts of the computer can be grouped into Input devices, the Processor and the Output devices.
a) Input devices : Key board, mouse, joystick, scanner, bar code reader etc. are called input devices. Data and instructions need to be entered into the memory of the computer to perform various tasks. . The input devices enable the users to input the data into the system which is processed in the processor and delivers the output.
b) Output devices : These are the devices through which the computer can provide the
results to the user. Printers, Monitor etc. are output devices.
c) Central Processing unit (CPU) : All the computing in a computer is done by the Central Processing Unit and the Main Memory of the computer. This is the brain of the computer. The input from the input devices is fed into the CPU for processing. The CPU uses software to process this input and sends the output to the output devices. CPU consists of two parts viz.,
(i) Arithmetic and Logic Unit (ALU) and
(ii) Control Unit
Arithmetic and Logic Unit (ALU) : It is the part of the CPU that does all the arithmetic and logical operations like addition, subtraction, multiplication, division operations such as X >Y etc.
Control unit : It coordinates all the operations of the computer. It controls the input and output devices, the ALU and the memory. It also ensures that instructions in the software are carried out.
Memory Storage : The memory storage is of two types.
(1) Primary Memory and (2) Secondary Memory.
Primary Memory : This is the main memory of the computer and is linked to the CPU and is
part of the base unit. RAM and ROM are different divisions of the primary memory.
a) Read Only Memory (ROM) : This is meant for information that is permanently required to run the computer and will remain, even if the computer is switched off. This is important because it contains all the information that the computer requires to start up.
b) Random Access Memory (RAM) : This is used for temporary storage. All the data and programs required for running a process are stored here, until
the process is over. More RAM storage space can make the computer work faster. All the data o the RAM is lost when the power is turned off.
Secondary Memory : All the data and programmes which are not running on the CPU are stored in the secondary memory. They are copied into the RAM whenever they are required.
The commonly used secondary memory storage devices are disks and tapes. There are three types of disks‐ Hard Disk, Floppy Disk and Compact Disk. Hard disks are fitted into the computer whereas the floppy disks, compact disks can be taken out and kept outside. A floppy can hold only 1.44 MB of information whereas compact disks can hold about 600 MB of data.
The floppy drive is referred to as ‘A’ drive. If there is a second floppy drive on the computer it is referred to as ‘B’ drive and the hard disk is termed as ‘C’ drive. The alphabets D,E, F etc., are reserved for additional hard drives that the computer may have.
Some storage devices. :
1. Floppy disk – 3 ½ inch diameter (previously we had 5 ¼ inch floppy disks also) : It is divided into concentric circles called tracks and the tracks are further divided into sectors. There is a small hole on the disk called index hole which denotes the starting point of the first sector. The 3 ½ inch floppy disks can store 1.44 MB or 2.88 MB of information.
2. Hard Disk : The disk consists of a disk pack containing hard disks/platters stacked onto
one another. A single hard disk is made of metal and coated on both sides with
metallic oxide. Hard disks can store large volumes of data as compared to floppy disks. Today we can see hard disks of capacity of 40 GB to 200 GB and even more. Portable (external) hard disks are also available now.
3. Digital Audio Tape (DAT) : This is widely used in our Bank for taking backups particularly in Bankmaster branches. It looks like an audio cassette and can store large volume of data ranging from 2 GB to 20 GB and even more.
4. CD ROM : These are also widely used now‐a‐days for data storage, storing music, video (cinemas) etc. Compact Disk (CD) can store up to 700 MB of data on it. Rewritable CDs are also available. This is a form of optical storage.
5. DVD (Digital Versatile Disk) : DVDs also look like CDs but can store much more data than that in CD. They can store 4.7 GB data on it. Dual layer DVDs can store almost double the data that can be stored on a normal DVD (single layer) i.e., up to 8.5 GB. Data recording is accomplished by burning the laser beam on CDs and DVDs.
6. Pen Drives / Flash Drives : These are also storage media ranging from 256 MB to 8 GB and more. These are very small and portable and easy to carry volume of data.
and more. These are very small and portable and easy to carry volume of data.
9. Explain about ‘software’.
Software : Computer can not work on its own. It must be given instructions in sequence to
work. Such instructions in any computer language is called a computer programme. Software
refers to the set of programs that control the activity of processing by the computer. The
computer software is classified into two broad categories –
a) Application software : Also known as application packages. This is a set of one or more
programs that are developed or written to do a specific job. Eg. An application package of
a company to process its sales data and to generate various sales reports.
b) System software : Set of one or programmes which are developed to control the
operation of the computer system. These programs do not solve specific problems but
they are general programs which help the user in the use of the computer system.
Hardware and software of a computer are interdependent on each other. They are like the two
sides of the same coin. The hardware cannot work on its own and the software cannot be
used without the hardware.
10. Explain about ‘Operating Systems’.
We need a ‘system’ (a software program) which helps us to use the computer effectively and efficiently. Such a software programme is called “Operating System” (OS) software. Operating
System falls under the category of system software. A computer cannot function without an operating system. The OS is the means by which a user can communicate with the computer.
All input and output devices, all actions and processes inside the computer are controlled by the OS. The OS communicates the user’s instructions to all the parts of the computer.
An operating system is a set of programs designed to manage the entire operations of a computer system. It does not do any specific work but it is a general program which assists the user by doing the following operations.
• controlling all of the operations including input/output operations, arithmetic operations
and internal movement of information.
• Communicating with peripheral devices (printers, disk and tape devices).
• Supporting the running of other software.
There are many operating systems like Unix, Linux, Mac, MS‐DOS, Windows etc.
11. Explain about ‘Microsoft Disk Operating System’ (MS‐DOS).
MS‐DOS is one of the most popular operating systems. Let us now have a look at some important MS‐DOS commands.
The command prompt : When you first turn on the computer, you will see some cryptic information flash by. When the information stops scrolling past, you will see the following :
This is called command prompt. The flashing underscore next to the command prompt is called the cursor. The cursor shows where the command you type will appear. DOS commands can be entered and executed one at a time from the DOS prompt. The commands can be typed either in lower case or upper case. You must press ‘enter’ key after every command you type.
DOS commands are basically two types. They are ‐‐
A) Internal Commands : These are a few special commands that are automtically loaded into
the computer memory when the system is booted. Some important internal commands are listed below :
B) External commands : These are some of the DOS commands that are stored as files on the DOS system disk.
Some important and commonly used commands are briefly explained below:
1. DIR (Directory) : Displays a list of the files and subdirectories that are in the directory you specify. When used without parameters or swithces it gives the particulars such as file extension, file size in bytes, date and time the file was last modified, total number of files listed, their cumulative size and free space remaining on the disk.
2. MD or MK DIR (MAKE DIRECTORY) : Used to create another directory in the drive in which we are working presently.
3. CD (CHANGE DIRECTORY) : We can switch over in to another directory from the present directory with the help of this command.
4. TYPE : With the help of this command we can view the contents of a file.
5. REN (RENAME) : Used to change the name of a file.
6. DEL (DELETE) & ERASE : to delete unwanted files from the directories this command is used. This command can be used in the following way.
7. RD or RMDIR (REMOVE DIRECTORY) : Used to remove the directory permanently from the computer. Syntax at the prompt is : RD
8. COPY : This is one of the most useful commands. To copy a file from one place to another place this command is used. Also used to store files on to floppy disks.
9. DATE and TIME : These commands are used to see the current date and time. The date and time can also be changed using these commands if necessary.
10. FORMAT : Creates new root directory and file allocation table for the disk. It can also check for bad areas on the disk and it can delete all data on the disk.
11. UNFORMAT:Restores a disk that was erased by using ‘Format’ command.
12. DISKCOPY : Copies the entire contents of one floppy disk to another floppy disk. Diskcopy writes over the existing contents of the destination disk as it copies the new information to it.
13. XCOPY : Copies directories, their subdirectories and files except hidden and system files. With this command, you can copy all the files in a directory including the files in the subdirectories of that directory. XCOPY source [destination]
14. SORT : Reads input, sorts data and writes the results to the screen, a file or another
device. SORT acts as a filter reading characters in a specified column and rearranging them in ascending or descending order.
15. TREE : Graphically displays the structure of a directory.
16. EDIT : Starts MS‐DOS editor, a text editor which is useful to create and edit ASCII text
files. MS‐DOS editor is a full screen editor that allows you to create, edit, save and print ASCII text files.
17. DELTREE : Deletes a directory and all its files and subdirectories.
18. FIND : Searches for a specific string of text in a file or files.
19. HELP : Starts MS‐DOS help.
20. MOVE : Moves one or more files to the location you specify. Can also be used to rename files and directories.
21. PATH : Indicates which directories MS‐DOS should search for executable files (programs).
22. PRINT : Prints a text file.
23. SCANDISK : Checks disks for damage and repairs them, if needed.
24. DEFRAG : Recognises the files on a disk to optimise disk performance. (This command
shall not be used while you are running Windows .)
25. CLS : Clears the screen.
12. What are wild characters?
WILDCARDS : A wildcard is a character that can represent one or more characters in a file name. If you want to carry out a task for a group of files whose names have some thing
common, you need not use the same command repeatedly for each file name in the group. Wildcards can be used to specify groups of files. Two wildcards are used in MS‐DOS. They are `*’ (asterisk) and `?’ (question mark). The `*’ represents one or more characters that a group of files has in common whereas the `?’represents a single character that a group of files has in common.
*.txt ‐ represents all files having a “.txt” extension.
letter.*‐ all files named “letter” with any extension R*.* ‐ all files beginning with letter ‘R’ regardless of their extension ????.* ‐ all files having four‐letter names with any or no extension. If `*’ is used, when you specify a file name, MS‐DOS ignores letters that come after the `*’ up to the dot (.). Eg. *m.exe would have the same result as *.exe has. Similarly, if the `*’ is used in the extension, DOS ignores the letters that apper afterward. Eg. Letter.*xt would have the same result as letter.*.
13. Explain about the ‘Windows’ operating system.
This is a simple Operating System to learn and use. The user need not memorise or type many commands. We find small pictures called icons on the screen which can be used to run programs. This is called GUI (Graphic User Interface). Microsoft Inc. of USA developed the Windows Operating System. It has undergone many versions such as Windows 95, Windows 98, Windows ME, Windows 2000, Windows XP and the latest version is Windows Vista.
When we switch on the computer, the OS is the first software programme that is loaded. This is called booting. After the process of booting first the Windows opening screen and then another screen called Windows Desktop appears. The small pictures on the desktop are called icons. The icons represent application software that are stored in the computer.
The name of the program is written below the icon.
At the bottom of the desktop we find a grey coloured strip called task bar. On the left of the task bar is a button named Start. The right side of the task bar shows the time. The task bar shows all the programs that are currently running on the computer.
Mouse : We find an arrow shaped pointer on the screen, the movement of which is controlled by moving the mouse. The mouse has two buttons on it. Clicking the left button once indicates a choice or selection. Clicking the left button twice in rapid succession causes the selected application or command to run or begin operation
When we click on the start button on the task bar, a box with a list of options opens up. This is called a Menu. As you move the mouse over the choices in the menu, the item below the pointer is highlighted.
Window : A window is the part of the desktop that is used by an application software. All application programs that we use will have a window.
A window has six important parts.
• Title Bar ‐ contains minimize, maximize, close buttons
• Menu Bar ‐ contains menus with options for different tools
• Tool Bar ‐ contains icons of the tools of application which Are frequently used.
• Large empty white portion ‐ actual working area
• Status Bar ‐ at the bottom of the window.
Files & Folders : When you draw a picture or write a letter using a computer, this picture or letter is stored in digital form as a file. A file is a unit of stored data or programs. It has a file name and a type for identifying it. The names may contain file extensions.
A collection of files kept together is called a folder. It can contain files of many types. Just as files, folders also have names. Folders do not have extensions. A folder can have subfolders inside it. (Sub‐folders are folders within folders.)
Windows Explorer : Windows explorer is an application in Windows 98 which is very useful