The basic structure of a computer
The basic structure of a computer
Normally a computer performs five basic tasks, viz, inputting, storing, processing, controlling and out putting.
Inputting is the process by which the computer accepts data and instructions. Storage of such data or instructions for use at the appropriate time is strong.
The activity of converting into facts the data given to a computer through inputting, is called processing. Outputting is the supply of these facts at the user's demand.
Main parts of a computer
A computer has the following parts :
- Monitor
- Central processing unit (CPU)
- Floppy disk unit
- Hard disk
- Key board
- Printer
- Mouse
1. Monitor or screen
The monitor, technically known as the visual display unit (VDU), resembles a tv screen. Monitors come in various sizes and are available in black and white and colour. The normal size of a monitor is 14". The monitor is provided with an on - off switch. The data we feed in the computer using the key board is displayed on the monitor. Normally a monitor displays 24 lines at a time. When the computer is switched on. the monitor displays a sign (c:>) which is clear indication that the computer is in a perfect working condition. As soon as the system (computer) closed the sign is also disappeared.
2. Central processing unit (CPU)
The most important part of a computer is its CPU. It can be considered the brain of the computer. Its primary function is to store and process the data that has been fed into the computer.
A CPU consists of three essential parts:
a. Arithmetic and logic unit (ALU)
Mathematical calculations are carried out at this unit.
b. Control unit
This unit contrls the overall functions of a computer. Like the brain, controls unit sends electronic signals to various components of the computer according to the instructions given.
c. Memory
This component of the CPU stores the matter that is fed into the machine. As the storing capacity increases the working efficiency of a computer also increases. The memory of a computer is measured in terms of bites. Memory can be classified into two types.
Primary memory
This forms a part of the internal structure of a computer. Primary memory again is divided into two :
Read only memory (ROM)
It is a constant set of data stored permanently. The data stored in ROM cannot be changed or altered. It remains unaffected even at the time of power failures. When we open the system it is the ROM that activates the computer as well as checks the memory.
Random access memory (RAM)
It is a temporary set up for storing programs and data. Unlike ROM the information / data can be updated in RAM. When the power is cut- off the information / data is lost. This shows the temporary nature of the memory.
Secondary memory
Secondary memory is the extended memory of a computer. It refers to the data / information stored in computer peripherals such as a magnetic tapes, compact disks, hard disks, floppy dist etc. Compared to the internal memory much more information can be stored in the extended memory.
3. Floppy disk unit.
Floppy disk is a thin, round - shaped plastic sheet coated with magnetic - chemicals.
Different parts of the floppy are
Write protected notch
a. It is a device to prevent manipulation of the data recorded in a floppy. WPN is a small gap on the corner of a floppy. Once this gap is closed, nobody can add or delete anything in the floppy. We can however see the data with out any hindrance.
b. Read write notch
It is a notch located in the centre of a floppy, touching this notch might damage the floppy disk. This is the part where the computer records and later reads the matter.
4. Hard disk
It is another important component of the computer, in which large quantity of data can be stored. It is created by arranging a bunch of floppies on an axle which are placed equi - distant to each other. As the number of floppies increases, the storage capacity also increases. Hard disk is located in a dustproof cavity
5. Key board
Yet another important component of a computer is the key board. It was invented by a German national, Conrad News. Various types of key boards are available in the market today with as many as 100 to 105 keys. When a key is pressed, it emits electric waves and these waves reach the computer. These electric waves give instructions to the computer and the computer starts functioning.
The keys on a computer key board can be divided into four categories. They are
- Typewriter keys
- Function keys
- Cursor keys
- Special purpose keys
a. Typewriter keys
Similar to a typewriter the keys are marked with the alphabets, single digit numerals and has signs like comman, full stop, colon, semi - colon and arithmetical signs.
b. Function keys
There are 12 function keys, marked F1 TO F12. Each key has a specific function and can be used while working on the computer.
c. Cursor keys
The eight keys on the right - hand side of the key board are the cursor keys. These control the cursor movement. Four of these keys are marked with a single arrow, each in four different directions. Movement of the cursor corresponds with the direction of the arrows. Other four keys and their functions are given below :
- Pgdn : Using this key we can move down through the pages in a file.
- Pgup : This key helps to go up through the pages in a file.
- Home: On pressing this key we can go back to the beginning of a program
End : We can bring the cursor to the end of the current life.
D. Special purpose keys
a. Capslock key
When pressed, this key gives the impressions of capital letters. It is a toggle key and can be pressed again to cancel the capitals and revert to small letters.
b. Shift keys
There are two shift keys on a key board located at both ends. Both the key serve the same purpose. Most of the keys on the key board are superscribed with two signs. Normally, on pressing a key the monitor shows the lower sign superscribed on the key. But when we press the shift key and then type, the monitor displays the upper sign on the key. For example, colon and semi colon are marked one below the other on a single key. When we apply the shift key and press we get the upper impression (ie) the colon (:). On the other hand when we type 'a' - pressing the shift key we get capital A. Here, the shift key functions as a capslock key.
Thus, if not for the advantage offered by the shift key, the size of our computer key boards may have had to be doubled.
c. Control key
This key is marked as ' Ctrl' . Several keys on the key board represent certain functions but they cannot perform these functions on their own. To get these functions done, we have to press the 'Ctrl' key first and then the required key. For example : Ctrl + p.. gives the command to print matter. Control key is mainly used in packages like wordstar.
d. Alternate keys
This key is marked with the abbreviation - 'Alt'. Its usage varies from program to program. Its operation is similar to the 'Ctrl' key. When we press the 'Alt' key followed by a particular key we may get a window with a list of the concerned details.
e. Enter key
It is also known as the return key. Enter key is the most pressed key in computer operations. This key is used after every entry or command and at each stage of the work on the computer.
f. Numeric key pad
This portion of the key board functions like a calculator. Normally there are 17 keys in this section.
g. Print screen key
Matter seen on the screen can be printed using this key
h.Escape key
As the name indicates this key is an escape from operational faults. If we type or give wrong comands, it is often possible to cancel the same by pressing the escape key (ESC) immediately after.
i. Space bar
The forward movement of the cursor is brought about by the space bar, the longest key on the key board.
j. Tab key
Tab key is used for moving the cursor to a fixed distance. In some programs tab key helps to change options also.
k. Pause key
If you want to pause while the computer is performing some function, just press the pause key. Another press on the pause key will restart the function.
l. Delete key
As the name indicates this key is used for deleting unwanted data.
6. Printer
Printer is an output device. It connects the coded matter stored in the computer and prints it in a form that can be read and used. It can print the matter directly from the screen or memory. Print outs helps us to analyse the matter that have been stored and processed into the computer.
Following are the four main type of printers :
1. Dot matrix printer
In this printer the characters are printed by patterns of dots. Dot matrix printer is usually used with personal computers.
Line printer
One complete line can be printed at a time on a line printer. This gives accuracy and speed to the printing process. Line printer is ideal to print large quantity of material at a high speed.
Ink-jet printer
It is the most commonly used multicolour printer.
Laser printer
Laser printer give the maximum clarity to the characters and is the most expensive among all the printers mentioned above
7. Mouse
The mouse is a very handy and helpful input device. As far as commands and instructions are concerned, mouse is a smart alternate to the key board. As the name indicates this tiny equipment is mouse shaped. It is rolled on a ball called the mouse ball. When we move the mouse, the indicator and pointer on the screen also move accordingly. To get a work done one has to fix the pointer on a particular command and click the mouse. There may be two or three switches on a mouse. Serial mouse and bus mouse are two varieties in use. The mouse makes the computer operations esay and often speed. A scientist named Gluss Angel Bart invented the mouse.
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