Keyboard

Keyboard

              The most common input device is the keyboard. The keyboard allows a user to communicate with the PC through keystrokes that represent character data and commands. Virtually every PC sold has a keyboard included as a part of its standard package. In fact, most people take their keyboard for granted and rarely even think about it.

Keyboard 

Keyboard Elements

             Most keyboard layouts are still a variation on the key layout of a typewriter, at least for the alphabetic, numerical, and special character keys, All keyboards have a core  component of keys founded on the keyboards of a particular continent (North America, Europe, etc.), country (France), or language (Chinese). However, keyboards also include a variety of other keys that are dedicated to specific functions or are assigned functions by the software running on the PC, such as a keyboard's function keys. A keyboard's keys can be grouped into functional groups.

1. Alphabetic keys: The alphabetic keys along with the row numbers and special characters. These keys match those on a typewriter.

2. Cursor control keys: Located to the right of the alphabetic keys, this group keys has two smaller groups of keys: the cursor function keys and the cursor arrow keys.

3. Function keys: Typically located across the top of a keyboard today, they were once located on either side of a keyboard. Current keyboards have 12 function keys,while most older keyboards have 8.

4. Number pad keys:  The number pad, which is located on the extreme right side of nearly all modern keyboards, contains keys for ten numbers, as well as the four arithmetic functions. The number pad can also be used as a cursor control pad by toggling the NUM LOCK key.

Cursor Control Keys

            The NUM LOCK key was used to toggle and lock the number pad between these two functions. On the 101-key design and those that followed, a set of four dedicated cursor control (arrow ) keys and a six-key set of cursor action (a.k.a. navigation)keys were added between the alphabetic keys and the number pad. This group of keys includes:

1. Cursor control (arrow) keys: 

            This group of four directional keys is used o move the cursor left, up, down, and right. Virtually all software supports the use of these keys. Game software relies on these keys to move characters through scenes using points of the compass represented by these four keys where up is north, down is south, left is east, and right is west. Some keyboards add four diagonal direction keys that move the cursor (or the action) in directions between the standard four keys.

2. Cursor command/Navigation keys: 

            A group of six keys located to the right of the alphabetic keys and above the cursor control keys, these keys, duplicate the six control functions originally included in the number pad's cursor control keys. The keys included are INSERT, DELETE, HOME, END, and PAGE UP and PAGE DOWN. The function of each of these keys is as follows:

I. INSERT:

           This is locking key that toggles software between insert and peplace modes. Insert mide, which is the default mode for most word processing systems, inserts characters at the point indicated by the cursor. Replace mode, which is also called type over mode, replaces any existing characters with the characters being entered.

II. DELETE:

            The function of this key is controlled by the software application running on the PC, but it is essentially used to remove a single character to the right of the cursor or a selected object.

III. HOME and END:

            In most applications, the HOME key positions the cursor at the beginning of a text line. The End key does the opposite and moves the cursor to the end of a text line. When used in combination with other keys, such as the CTRL key, the HOME key moves the cursor to the  beginning of a document, and the End key moves the cursor to the end or bottom of a document.

IV. PAGE UP and PAGE DOWN:

            These keys are used primarily in document-based software to scroll one entire screen up or down. On many keyboards they are labeled PG UP and PG DN.

The Number Pad

            Every one of the keys on the number pad can be found elsewhere on the keyboard. This set of keys was originally added to the keyboard to facilitate the entry of numeric data. It replicates the key placement used on a ten-key calculator or cardpnch machine. Most users simply ignore it, but for those users who must enter large volumes of numeric data, the numeric keypad is an absolute necessity. The keys included in the number pad are as follows:

           NUM LOCK: This key is used to toggle and lock the cumber keypad between its function as a number pad and its cursor control function. The default setting (on or off) for the NUM LOCK is set in the PC's BIOS settings. Virtually all systems set the NUM LOCK on during the boot and leave it on, ignoring the cursor control functions of the number pad.

         Arithmetic operators:  The number pad includes keys for the four standard arithmetic operators,/(divide), * (multiply),-(subtract), and + (add).

Function Keys

            The 12 keys on the top row of the keyboard are the function keys. These keys have no default functions and are completely controlled by software, whether it is the operating system or an application. Some software applications make extensive use of the function keys, such as WordPerfect (a word processing system from Corel). For example, on the DOS and Windows command line, the F3 key All function keys are designated with an F to differentiate them from the number keys) is used to repeat the last line entered, and in virtually all Windows applications, the F1 key is used to open the Help system. The earliest PCs had ten function keys that were arranged to the left side of the keyboard is two columns of five keys. When the enhanced keyboards were introduced, the keys were expanded to twelve keys and placed along the top edge of the keyboard.

Special-Purpose Keys

            A few other keys on the keyboard are used only for very special purposes, if at all. Some users rarely or never use these keys because not all applications support them or their functions just do not come up in most data processing situations. These special-purpose keys are:

• Esc: The Escape key is typically enabled as an exit key by most software applications. It is used to cancel out of a command or to exit an application. It is also used in combination with other keys to create special key values and to indicate other actions. For Example, in Windows the ESC key can be used to close a context menu.

• Print Screen/SYSRQ: The PRINT SCREEN mode of this key got its name back in the MS-DOS days, when pressing it sent the image of the display to the pronter. On a Windows system, the image of the monitor's display is  sent to the Windows Clipboard. The alternate mode of this key is a system request action. This key has no real function on most PCs unless the PC is emulating an IBM terminal connected to a mainframe computer.

• Pause/Break: In its default mode (PAUSE), this key will, if enabled by software, pause the display or the action of an application program. It used in combination with the CTRL key, the alternate mode of this key interrupts or halts some software programs, primarily MS-DOS commands and applications. Using the CTRL and BREAK keys together is the same using the CTRL and C keys to break an action.

Keyboard Connectors

     Keyboards attach to a PC through one of four connector types:

• 5-pin DIN connector: This connector, often called the AT style connector, has been in use since the very first PCs. DIN is a German standards organization that developed the round connector style used on this and the 6-pin version of this connector. Only four of the five pins are used; they carry the clocking (pin 1) and data (pin 2) and provide a ground (pin 4) and +5V of power (pin 5). 

• 6-pin mini-DIN (PS/2) connector: This is a smaller DIN connector that uses four of the six pins to connect the data signal (pin 1), ground (pin 3), +5V of power (pin 4), and a clocking signal (pin 5). This connector, which is now the de facto standard for all cabled keyboards, was first introduced on the IBM PS/2, Which is why it is commonly referred to as the PS/2 connector.

•  USB (Universal Serial Bus) connector:  Many keyboards (and  mice) are now available with a USB connector. This type of connector is especially useful when your notebook computer has only one PS/2 port and you wish to connect both a keyboard and mouse to it.

•  IrDA (infrared) connector: Several keyboard styles are available with an infrared (wireless) interface. Several models of full-sized and even multimedia keyboards are available for use with either desktop or notebook PCs that support the Infrared Data Association (IrDA) standard interface.

•  Radio frequency (RF) connection: The most common form of cordless devices uses digital radio technology to connect a keyboard (or mouse) to the PC. The advantages of RF cordless devices include that they do not require a line of sight to work and have a range of up to six feet from the receiver. The keyboard actually communicates to the PC through a transceiver unit that attaches to the PC through either a PS/2 or USB port. The transceiver usually has a five-to six-foot cord with it so that it can connect to the port in the rear of the PC and still sit in front of the PC.