Organization of a Computer:-
A computer is fast and accurate device, which can accept data, store data, process them and given, desired results as output. The computer is process them and given, desired results as output. The computer is organized into four units such as, Input unit CPU, Secondary memory and Output unit as show in the following diagram.
A hardware device that accepts inputted information and also has the capability of outputting that information.
Input Unit:-
Any device designed to assist in the entry of data into a computer is known as Input devices. Input devices convert data from any convenient external format into binary codes that a computer can store and manipulate internally, Some of the most common, most popularly used devices are discussed below.
1. Mouse:-
This Input device is categorized as a pointing device because it is used to point and select an option on the monitor. It is small boxlike object that is connected to the computer by a cable and can be rolled around on the table. A pointer on the screen follows the movements of the mouse; rolling the mouse left moves the pointer left by an equipment amount, rolling the mouse in the right direction moves the pointer in the right direction, rolling the mouse in the up direction moves the pointer in the up direction, rolling the mouse in the down direction moves the pointer in the down direction and you can roll the mouse in a angular direction also. In order to select an option on the computer screen, the user should move the pointer at the desired position and press the button on the mouse. The mouse can be used to open menus, select texts for editing, move objects on the screen draw images or diagram etc.
A mouse can be classified on the basic of the number of buttons it has, the technology it uses, and the kind of interface it shares with the computer, A mouse may have one, two or three buttons. The program that uses the mouse determines the function of each buttons. A mouse may be classified as Mechanical mouse and an Optical mouse, on the basis of the technology it uses. In a Mechanical mouse, the rubber-coated ball that projects through the bottom surface rotates as the mouse is moved along a flat surface and sends electrical signals to the system unit by means of switches inside the mouse, This cursor the cursor, or pointer, to move in a corresponding fashion. An Optical mouse uses diodes to emit light beam instead of a rotating ball to detect movement across a specially patterned metal pad.
2. Light Pen:-
This is also categorized into a pointing device, which can be used only with video displays .It can be used to select an option by simply pointing at it, or drawing figures directly on the screen . An electron beam that repeatedly scans the display screen from left to right and from top to bottom produce a video display. Because of this scanning action, each point on the display is illuminated at a slightly different time.
The light pen, which is a pen like device, has a photo detector at its tip. The detector can detect changes in the brightness of the screen. The light pen is connected to the computer by a cable. when the pen is pointed at a particular spot on the screen, the point is scanned and the photo detector records changes in the brightness and sends electrical pulses to the computer. The computer can find out the extract spot with this information, Light pens are useful for menu-based applications. It is also useful for drawing graphics in Computer Aided Design software.
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