POINTING DEVICES


A Serial Mouse.

In the days of DOS a computer user had to remember which command to type, or at best which function key to press, in order to make the computer DO something.

There were templates which fitted over the function keys to remind the user what each one did, but any given function key did something different in each application. Eventually the F1 key became the 'Help' key in nearly all applications, but the others were all different. As you might imagine this led to some confusion when an operator used an application which he or she was not usd to. Also a lot of training was required in order to learn how to quickly and effectively use an appication.

The advent of the mouse changed all this. A drop down menu system was developed which meant that you could just point to the function you required, and click it with the mouse; further related options would then appear, and you pointed to the one which you required and clicked the mouse button to execute it. This system is still in use today. The advent of windows and a mouse greatly improved the useability of a PC. The user just points to an icon (a small picture representing the application or action) and clicks the button. No more remembering what each button does! Windows 95, 98, NT & 2000 automatically recognise when a mouse is connected and the relevent drivers are loaded automatically. In the DOS environment the software drivers for a mouse have to be loaded manually.

There are two types of mouse connector. One is connected to one of the PC's SERIAL ports with a 9 pin d-type plug and the other uses the little round PS/2 connector. They are known as a SERIAL MOUSE and a PS/2 MOUSE respectively.

There are other pointing devices available, namely track balls and graphics tablets. Track balls are like a mouse upside down: a ball is exposed in the top of the unit and two buttons are located in a convenient place. The user rolls the ball in order to move the pointer on the screen and presses the button as on a mouse.

Graphics tablets are large (relatively) flat devices. The flat area represents the screen area and you touch the tablet with a wand, or in some cases just your finger, in order to move the screen pointer. There are two types of tablet: absolute and relative, i.e. with an absolute tablet if you touch the top left of the flat area the screen pointer jumps to that position. The relative type works slightly differently; if the screen pointer is at the bottom right of the screen you would touch the tablet anywhere and drag your wand in the direction which you want the pointer to move. It does not represent the position of the wand it only follows the wand's movements. There are usually no buttons on a graphics tablet, you just tap the tablet with the wand to simulate pressing a button.