3.6. Input devices

The main standard input device in the PC is the keyboard. In its case there are key sensors, decoding circuits and a microcontroller. Each key corresponds to a specific sequence number. When pressing a key, information about this is transmitted to the processor in the form of a corresponding code. This code is interpreted by the driver - a special program that accepts characters entered from the keyboard.

There are keys on the keyboard that do not send any code to the processor and are used to switch the status of special signs of the keyboard status.

To save space in portable and pocket PCs, keyboards with a small number of keys are used.

The layout of the keys on the keyboard corresponds to the standard Latin typewriters.

Coordinate manipulators are coordinate input devices. These include mice, trackballs and pointers.

The mouse is connected to the computer via the serial port. When you move the mouse, information about the type of this movement is transmitted to the driver, which changes the location of the mouse cursor on the screen. Due to this, it is possible to report the current values ​​of its coordinates to the application program. The mouse plays a special role when working with graphic information in graphic editors, computer-aided design systems. The most commonly used left and right mouse buttons. Usually, programs track one- and two-click of the left mouse button, as well as a single click of the right mouse button.

Trackball is a ball embedded in a keyboard that differs from a mouse in that it does not need to be moved around the working surface.

Pointer is an analogue of the joystick and is located on the keyboard.

Trackballs and pointers are most often used in portable computers, and in pocket computers, a touch screen is used as a coordinate input device.

Scanners are called input devices for graphic information in a computer. There are manual, flatbed and roll scanners; black and white and color.

Using a hand scanner, you must move it along the surface of the sheet from which the image is taken. Individual elements of the image can be entered in parts and combine them in the required sequence, using special programs.

Tablet scanners are easy to use, more productive than manual, and expensive. When working with such scanners, the book in expanded form is placed on the scanner plate, and he independently reads the entire sheet. These scanners have high resolution, so they are used to input photos and complex illustrations into the PC.

Roll scanners are also easy to use and are designed for continuous reading of information from roll media, for example, when analyzing experimental data.

Scanners can be divided into black and white and color. Black-and-white scanners are mainly used for scanning textual information, and color scanners are used for graphics.

Digitizers are devices for point-by-point coordinate input of graphic images that are used in computer-aided design systems, computer graphics, and animation. This device allows you to accurately enter complex images, such as drawings, maps, etc.

In terms of assembly, the digitizer is a tablet containing a work plane with a grid plotted on it. It has a control panel and a special light pen connected to the tablet. With a computer digitizer is connected by cable through the port.