Minding Your Keys and Qs
The keyboard is the main device you use to interact with a computer system. Your keystrokes are converted into the characters that you see on the screen and eventually print out. Most keyboards have five major key parts, or groups, that contain keys of a specific purpose.
The five major groupings on a keyboard are:
- Alphanumeric: The alphanumeric keys are the keys on the keyboard that contain the letters of the alphabet, numerals, and punctuation.
- Function: The 12 function keys on a keyboard offer special features. For example, in Windows, pressing the F2 keystroke is used to rename a file or icon.
- Cursor: The cursor keys allow you to move the cursor or insertion point around by using the keyboard.
- Numeric: The numeric keypad has the mathematical operators and numbers for quick, single-handed access for inputting numeric information.
- LEDs: The LEDs indicate whether features such as Caps Lock, Num Lock, and Scroll Lock are turned on or off.
Each key on the keyboard has a keyswitch that closes an electrical circuit on a grid when a key is pressed. When the key contacts the grid, the keyboard controller detects the keystroke and generates a keycode. The keycode is then converted into an ASCII code that is used to display the character on the screen.
Each location on the grid corresponds to a specific keycode. This is why you can't simply move the key caps around and expect to move the character that types. For example, the letter A is on the left side of the keyboard. Moving the A key to the right side of the keyboard will not allow you to press that key to type the letter A because the location on the grid that generates a keycode for letter A is on the left side of the keyboard.
The different keyboards work in different ways when you press a key. Each manufacturer decides what type of keyboard to manufacture and how the keystrokes will be interpreted by the system. The two most popular techniques used to identify what keys are being pressed are as follows:
- Switch-based: A switch-based keyboard uses micro-switches for each key. The downfall of a switch-key keyboard is that the keys deteriorate with time and tend to get dirty, but the good thing is that these keyboards are not expensive.
- Capacitive: A capacitive keyboard is also known as membrane keyboard and is more expensive than switch-based keyboards. Although a capacitive keyboard is more expensive, it is also more reliable. With a capacitive keyboard, each key pushes a spring, which pushes a paddle and creates an impression on the capacitive surface located under the keyboard. The impression on the capacitive surface sends a signal that is interpreted by the keyboard controller. This is the most common type of keyboard in portable computers.
In order for the keyboard to work with the system, there must be some software that drives the keyboard actions. Two types of software routines are used to allow the keyboard to work with the system:
- Keyboard device driver: Like any piece of hardware, there is a driver in Windows that is responsible for allowing the device to work in Windows - including the keyboard.
- Firmware: The keyboard firmware is typically stored in ROM in the actual keyboard (as in the case of the XT keyboard) or in a chip on the motherboard. The firmware contains low-level code to communicate with the hardware.