Keyboard:
Keyboard is the most common, familiar and most important input device. It looks like a typewriter. It has got various keys, which are used to give data and commands to the computer. Commonly, we use a standing QWERTY keyboard with letters arranged in the same order as those on a typewriter.
The most important thing to watch out for is the keyboard connector. If you build as ATX system, you’ll need a keyboard with a PS/2 connector, if you build an AT system, you’ll need one with a DIN connector (Germany’s Deutsche Industries Norm, a committee that set German Standard)
Most new keyboards you come across these days have a nice non-click touch and feel and are as ergonomic as possible, hence eliminating the need for a wrist pad. Click- keyboards are still available though if you prefer to “hear” your own stokes, but it will probably only drive you crazy. The difference between click and non-click keyboards is their design. Click keyboards are mechanical, whereas non-click keyboards use soft rubber membranes to close contact.
A USB keyboards is a computer keyboard which connects to the central computer system via universal Serial Bus port. It uses a separate scan code system to other types of keyboard.
Types of Keyboards:
Different types of keyboards are used with the IBM PC computers. With each new model of the PC such as PC/PC-XT, PC-AT etc., IBM introduces a new type of keyboard. The recent Enhanced PC-AT keyboard is now being used as industry standard by most of the computer manufacturers.
The following list gives a concise overview of the PC keyboard as it has changed over the years, the changes often being made at the launch of new PC versions.
1. 83-key PC/XT keyboard layout-original left hand side function key (F key) columns with 10 keys F1 through F10; electronically not compatible with the later keyboard types.
2. 84-key PC/AT keyboard layout-the “84th key” being <SysRq> i.e. System Request; numerical block now clearly separated from main keyboard; also added indicator LEDs for Caps/Scroll/Num lock.
3. 101-key “Enhanced” keyboard layout-additional navigation and control keys; 12 F keys in row along top, grouped F1-4, F5-8, and F9-12.
4. 102-kay “Enhanced” keyboard layout-(additional key to the right of the left Shift key for European layouts)
5. 106-key “Enhanced” keyboard layout-5 more keys added for input in Asian languages.
6. 104-key “Windows” keyboard layout-Windows(x2) and menu key added.
7. 105-key as above, but for European layouts.
8. 109-key as above, but for Asian layouts.
9. 107-key “Enhanced” keyboard layout-Power management keys were added So-called
“multimedia keyboards” may offer additional buttons to the 104 or 107 “standard” keys, often providing volume control, media player buttons, and miscellaneous user-configurable shortcuts, e.g. to email clients, web browsers, etc.
10. PC/PC-XT Keyboard
This design was kept as the IBM standard till the introduction of AT. It is equipped with total of 83 keys so, sometimes it is also called as 83-keys keyboard. It has two vertical rows of function keys at the left of main alphanumeric keypad. The cursor controls share the same keypad with a calculator-style array of numbers for direct data entry. The ENTER key is small and can be identified with a bent arrow legend. There are no LED indicators installed for the three locking keys: CAPS LOCK, NUM LOCK and SCROLL LUCK.
11. PC-AT Keyboard
The PC-AT keyboard was and improvements over the original PC, PC-XT keyboard. IBM tried to solve most of the problems associated with the original keyboard with the introduction of this new keyboard with their PC-AT range of machine.
This ENTER key is also increased and the word “Enter” is printed at this key top. Most of the keys that were indicated only with arrow symbols were also indicated with words describing them. In this keyboard, LED indicators are provided for locking shift Keys (Caps, Scroll, Num Keys). Other than this, the numeric keypad is moved away from the letters for easy access during the numeric data entry. Most of the keyboards in the market provide a XT/AT switch on the bottom side of the keyboard to configure the keyboard to be used with PC, PC-XT (8086/8088) system or PC-AT (80286) system.
This keyboard has 84 keys, so it is also referred as 84-keys keyboard.
12. Advanced / Enhanced PC-AT keyboard
After the introduction of the PC-AT keyboard, IBM made one more change into the keyboard layout and introduced an Enhanced PC-AT keyboard layout. One major enhancement in this layout is moving of Function keys to the top of the keyboard and providing additional cursor control keypads.
In this layout, all the ten function keys are moved to the top of the keyboard and also two more keys F11 and F12 were added to the existing keys. This keyboard had total 101 keys at first. But now a day, this keyboard comes with 104, 107 keys. The additional keys except 101 keys are two keys next to the alt keys, used to bring up the start menu, one key next to the right Ctrl key, used to bring up a menu of functions that are frequently accessed in whichever application is currently being used, Wake, Sleep and Power keys.
The 5-pin DIN (Germany’s Deutsche Industries Norm, a committee that set German standard) connector is the most common type of connector for PC, PC-XT and PC-AT keyboards. Whereas the 6 pin mini DIN connector is used for PS/2 keyboard and the Shielded Data Link (SDL) connector is used for the IBM’s Advanced keyboard.
The shapes of these connectors are different but they carry almost the same signal from the keyboard to the computer. One wire is used to send a keyboard clock to synchronize the keyboard logic with that of the computer. A second wire is used to carry the keyboard data to the computer in serial format. Third wire is unused. The fourth wire is used as a ground and it serves as a return line for the circuits in the keyboard and the fifth wire is used to carry the +5 V DC current to the keyboard.
A typical computer keyboard contains all letters, number, symbols of a regular typewriter, plus other keys which may include:
i. Number keys:
These are used for numerical calculation. It contains 0 to 9 and some numerical operators like +, -, *,/ etc.
ii. Function keys (F1 to F12):
There are used to perform a set of operation (mostly to give the commands to the computer) by a single keystroke.
iii. Special keys.
The special keys are used for specific tasks. Some of the special keys are Enter, Backspace, Del, INS, Shift, ESC, Alt, Ctrl etc.
Enter : It is one of the most important key on the keyboard. It is used to change the paragraph and to write the short text. It is also used to enter into the selected computer program by pressing it once.
Backspace : It is used to delete one character to the right of cursor. It is also used to delete the computer items.
Shift : It is used to capitalize the letters and write upper printed characters on every key.
ESC : It is used to close the dialog boxes and also to terminate the running process.
Alt : It is used to activate the menu bar and the close the current window with the help of some other keys. It is also used to define shortcuts for the computer applications.
Ctrl : Mainly it is used for shortcut keys to perform specific t ask inside the computer programs. It is also used to define shortcuts.
