Computer Keyboard is a character input device that enables the user to provide input to the computer for processing. A keyboard is a typewriter that uses the location of buttons. This is a set of input keys for a personal computer or terminal computer.
Input devices like a computer keyboard, scanner, pointing devices like a light pen, trackball, and touchpad are used to accept data and commands from the user and send it to the processor for processing.
The keys of a computer keyboard can be classified as
- Special keys – scroll lock, caps lock, function keys, control keys, shift keys, arrow keys, etc.
- Alphanumeric keys – All alphabets and all numbers
- Punctuation keys – semicolon, underscore, hyphen, full stop, etc.
Layouts of Computer keyboard
Keyboards are classified according to their format
- 83 key PC/XT keyboard
- 84 key AT keyboard
- Enhanced AT 101 key keyboard
- Windows 104 key keyboard
83 key PC/XT keyboard
This keyboard was originally introduced with the IBM pc .this type of keyboard was different from the other keyboards of those days, the keyboard was integrated and made as a part of the system unit could not be detached. It had ten functional keys namely F1 to F10 arranged in two vertical rows at the left side of the keyboard. There is no separate arrangement for numerical keys to the right of the keyboard. This type of keyboard is not electrically compatible with the other keyboards of later days.
This keyboard is obsolete and not used nowadays. This was used in the early IBM computers.
84 Key at keyboard
The keys present in 84 key AT the keyboard is mostly the same as the previous one. The major difference is that one key by name sys req is included in this layout. The numbers are clearly kept separate in this layout and the LED’s are introduced to represent CAPSLOCK, NUMLOCK, and SCROLL lock.
The 84 key AT Keyboard is compatible with all the other keyboard layouts introduced later. In this keyboard, the arrow keys are present along with the numbers and the separate cursor keys present in the modern keyboard are missing. The arrangement of keys looks better than its predecessor PC/XT keyboard.
Enhanced AT 101-key keyboard
The enhanced 101-key keyboard looks familiar to the recent computer users.
Following are the new features included in this keyboard layout –
- The dedicated cursor and navigation keys (arrow keys) are present at the right side of the keyboard.
- The position of the function keys is now made horizontal at the top rather than the keys arranged in two vertical rows of the previous types. The second ALT and the CTRL keys were introduced in this layout of the keyboard.
- The position of the <Esc> and the <Capslock> has been changed.
- Two new functional keys namely the <F11> and <F12> has been introduced
- There is a separate extra numerical keypad present to the right side of the keyboard.
Windows 104 key keyboard
The major difference between the enhanced 101 key keyboard and the windows 104 key keyboard is the introduction of the windows key at either side of the space bar key.
Since windows were the major operating system the shortcut key to windows was essential. Hence, Microsoft designed a new keyboard layout including the windows key.
Computer Keyboard interfaces
The keyboard uses the following signals for communicating with the computer
- Data – the data (scancode) sent by the keyboard circuit when you press a key, is transmitted bit by bit serially.
- Clock – it is sent from the keyboard to synchronize the data signals
- Power supply – keyboard circuit uses +5 V DC power supply form the motherboard to operate.
- Ground – provides signal ground for the interface
listing of some of the interfaces connect the keyboard are :
- 5 pin DIN connector
- 6 pin PS/2 connector
- USB interface
- IrDA interface
5pin DIN (Deutsche Industrial Norm) connector
The keyboard attaches through the computer using the keyboard connector.
|Pin#||5-pin DIN connector|
6 pin PS/2 connector
PS/2connector is an interface available to connect both mouse and the keyboard. This connector first applied on the IBM PS/2 computer system which used for laptops and desktops.
Each pin has its function. The table lists the functions of each pin
|Pin no||Pin name|
Universal serial bus (USB) keyboard
The USB type keyboard connects through the USB port.
The universal serial bus is a hardware standard that permits the user to connect the peripheral device directly to the USB port. The USB interface is stackable and swappable. stackable means any number of devices can be connected in a daisy chain. swappable means the device can be added/removed without turning off the computer.
Working of Computer keyboard
The designing of key switches in a keyboard is in many different ways. The output key connects through the electronics circuits. That results in fast encoding but it requires a lot of hardware circuits. This type of arrangement will support small keyboards found in calculators and electronic cash register. The large keyboards used in computers are using the matrix organization, which the popular technique in the market. Therefore, designing of each key is in a unique way.
Switches of Computer keyboard
The keyboard switches can be classified as mechanical switches and non-mechanical switches. The switch consists of two plates a movable plate and an immovable plate. On pressing a key, there is no direct physical contact but the circuit continues running. Again, On pressing a key, the space between the plates varies which causes a change in the capacitance value which in turn affects the current flow.
The following are the mechanical types of switches. They are-
- Rubber Dome
- Metal contact
- Foam contact
List of basic computer shortcut keys:
- Ctrl-B -> text bold
- Ctrl-I -> text italic
- Ctrl-U -> text underline
- Ctrl-A -> all text select
- Ctrl-C -> selected item copy
- Ctrl-X -> selected item cut
- Ctrl-V -> selected item paste
- Ctrl-Home -> any document move to the beginning
- Ctrl-End -> any document move to end
- Ctrl-Left arrow -> one-word move to the left
- Ctrl-Right arrow -> one-word move to the right
- Ctrl-Shift-Escape -> task manager
- Ctrl-F4 -> window close
- Ctrl +/- -> text/column size change
- Alt-F -> the file menu open
- Alt-F4 -> current program close
- Alt-Tab -> open applications switch
- Home -> move to the beginning
- End -> move to end
- Shift-Home -> move to the beginning of the line
- Shift-End -> move to end of line
- Delete -> files delete
- Shift-Del -> files delete permanently
- F1 -> help file open
- F5 -> Refresh