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. For each layout, some of the most significant updates are mentioned.
- 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
- 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 LED s for Caps/Scroll/Num lock
- 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
- 102-key "Enhanced" keyboard layout – (additional key to the right of the left Shift key for European layouts)
- 104-key "Windows" keyboard layout – Windows (x2) and Menu keys added
- 105-key as above, but for European layouts
- 107-key "Enhanced" keyboard layout – Wake, Sleep, and Power keys added (for Power Management )
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.
The PC keyboard with its various keys has a long history of evolution reaching back to Teletypewriter s. In addition to the 'old' standard keys, the PC keyboard has accumulated several special keys over the years. Some of the additions have been inspired by the opportunity or requirement for improving user productivity with general office Application Software , while other slightly more general keyboard additions have become de facto standards after being introduced by certain Operating System or GUI software vendors such as Microsoft .
''See also'': Modifier Key
- ''Shift'' selects the upper character, or select upper case of letters. The Shift key in typewriters was attached to a lever that moved the character types so that the uppercase characters could be printed in the paper.
- ''Caps Lock'' selects upper case, or if shift is pressed, lower case of letters. In mechanical typewriters, it worked like the Shift key, but also used a lock to keep the Shift key depressed. The lock was released by pressing the Shift key.
- ''Enter'' wraps to the next line or activates the default or selected option. ASCII keyboards had CR or " Carriage Return ". Typewriters used a lever that, once pressed, would move the cylinder with the paper.
- ''Ctrl'' shifts the value of letters and numbers from the ASCII graphics range, down into the ASCII control characters. For example, CTRL-S is XOFF (stops many programs as the print to screen) CTRL-Q is XON (resume printing stopped by CTRL-S).
- ''Esc'' produces an ASCII ESC character. Older software uses it to exit menus or modes.
- ''Tab'' produces an ASCII Tab character. Moves to the next tab stop.
- ''~'' is a ''tilde'', an accent backspaced and printed over other letters for non-English languages. Nowadays the key does not produce a backspaceable character and is used for 'not' or 'circa'.
- ''`'' is a ''grave'' accent, also formerly backspaced over letters to write non-English languages; on some systems it is used as an opening quote. The single quote ' is normally used for an acute accent.
- ''^'' is a circumflex, another accent for non-English languages. Also used to indicate exponentiation where superscript is not available.
- ''---'' is an asterisk, used to indicate a note, or multiplication.
- ''_'' is an underline, backspaced and overprinted to add emphasis.
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