IBM PC keyboard

The keyboards for IBM PC compatible computers are standardized. However, during the more than 30 years of PC architecture being constantly updated, multiple types of keyboard layout variations have been developed.

A well-known class of IBM PC keyboards is the Model M. Introduced in 1986 and manufactured by IBM, Lexmark, Maxi-Switch and Unicomp, the vast majority of Model M keyboards feature a buckling spring key design and many have fully swappable keycaps.

Keyboard layouts

The PC keyboard changed over the years, often at the launch of new IBM PC versions.

Name Keys Description Image
Model F (PC/XT) 83 Original left-hand side function key (F key) columns, F1 through F10; electronically incompatible with PC/AT keyboard types
83-key PC/XT keyboard
Introduced with original IBM PC August 1981.
Model F (PC/AT) 84 Additional Sys Req (system request) key; numerical block clearly separated from main keyboard; added indicator LEDs for Caps/Scroll/Num lock
84-key PC/AT keyboard
Introduced August 1984.
Model M (Enhanced) Additional navigation and control keys; 12 F keys in separate row along top, grouped F1–4, F5–8, and F9–12. Early models of Enhanced keyboard (notably those manufactured by Northgate Ltd.) maintained the layout with function keys on the left side, arranged in two columns of six pairs. This layout was more efficient for touch typists but was superseded in the marketplace by that with F-keys along the top. PS/2 released April 1987. There are different versions of the Enhanced keyboard layout:
101 standard US layout
101-key Enhanced keyboard
Introduced April 1986.[1]
102 European layouts
  • additional key to the right of the Left Shift key
  • different shape of the Return key
102-key Enhanced keyboard
Introduced April 1986.
103 additional 2 keys (one to the left and one to the right of the space bar) for the Korean layout
104 Brazilian ABNT NBR 10346 variant 2 (alphanumeric portion) and 10347 (numeric portion).
104-key Windows keyboard
106 additional 5 keys (one above the tab key, one to the left of the right Shift key, one to the left and two to the right of the space bar) for the Japanese layout
106-key Enhanced keyboard
Windows[2] Additional MS Windows key (×2) and Menu key added (one MS Windows key to the right of the left control key, the other and the Menu key to the left of the right control key).[2][3] Introduced in the Microsoft Natural keyboard for use with the MS Windows 95 operating system.[4] Most modern PCs, whether supplied with MS Windows or not, are now delivered with this layout.[5] Like the Enhanced layout, there are regional variants of the Windows keyboard layout:[5]
104 standard US layout
Modern 104-key Windows keyboard
105 European layouts[5] (as above)
105-key Windows keyboard
106 Korean layout (as above)
Modern 106-key Windows keyboard
107 Brazilian ABNT NBR 10346 variant 2 (alphanumeric portion) and 10347 (numeric).
Modern 107-key Windows keyboard
109 Japanese layout (as above)

Common additions to the standard layouts include additional power management keys, volume controls, media player controls, and miscellaneous user-configurable shortcuts for email client, World Wide Web browser, etc.

The IBM PC layout, particularly the Model M, has been extremely influential, and today most keyboards use some variant of it. This has caused problems for applications developed with alternative layouts, which require keys that are in awkward positions on the Model M layout – often requiring the pinkie to operate – and thus require remapping for comfortable use.[6] One notable example is the Escape key, used by the vi editor: on the ADM-3A terminal this was located where the Tab key is on the IBM PC, but on the IBM PC the Escape key is in the corner; this is typically solved by remapping Caps Lock to Escape.[6] Another example is the Emacs editor, which makes extensive use of modifier keys, and uses the Control key more than the Meta key (IBM PC instead has the Alt key) – these date to the Knight keyboard, which had the Control key on the inside of the Meta key, opposite to the Model M, where it is on the outside of the Alt key; and to the space-cadet keyboard, where the four bucky bit keys (Control, Meta, Super, Hyper) are in a row, allowing easy chording to press several, unlike on the Model M layout. This results in the "Emacs pinky" problem.[7]

Reception

Although PC Magazine praised most aspects of the 1981 IBM PC keyboard's hardware design, it questioned "how IBM, that ultimate pro of keyboard manufacture, could put the left-hand SHIFT key at the awkward reach they did".[8] The magazine reported in 1982 that it received more letters to its "Wish List" column asking for the ability to determine the status of the three lock keys than on any other topic.[9] BYTE columnist Jerry Pournelle praised the keyboard's feel as "excellent" but complained that the Shift and other keys' locations were "enough to make a saint weep", and denounced the trend of PC compatible computers to emulate the layout but not the feel.[10] He reported that the layout "nearly drove" science-fiction editor Jim Baen "crazy", and that "many of [Baen's] authors refused to work with that keyboard" so could not submit manuscripts in a compatible format.[11] BYTE's review was more sanguine. It praised the keyboard as "bar none, the best ... on any microcomputer" and described the unusual Shift key locations as "minor [problems] compared to some of the gigantic mistakes made on almost every other microcomputer keyboard".[12]

"I wasn't thrilled with the placement of [the left Shift and Return] keys, either", IBM's Don Estridge stated in 1983. He defended the layout, however, stating that "every place you pick to put them is not a good place for somebody ... there's no consensus", and claimed that "if we were to change it now we would be in hot water".[13]

Standard key meanings

See also: Modifier key and Lock key

The PC keyboard with its various keys has a long history of evolution reaching back to teletypewriters. 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 the factory standards after being introduced by certain operating system or GUI software vendors such as Microsoft.

From mechanical typewriters

From Teletype keyboards

Invented for computers with video displays

Connection

System Connector Pinout Transmission Protocol Command Strings Image
PC (Type 1) [16] 5-pin DIN
(DIN 41524)
1 CLK

2 DATA
3 -RESET
4 GND
5 +5V

2 start bits,
8 data bits,
make/break bit (keydown/keyup),
1 stop bit

keyboard reset via pin 3 to ground

Not supported
5-pin DIN connector
XT (Type 2) [17] 5-pin DIN
(DIN 41524)
1 CLK

2 DATA
3 N/C
4 GND
5 +5V

2 start bits,
8 data bits,
make/break bit (keydown/keyup),
1 stop bit

keyboard reset via sequence on DATA and CLK lines

Not supported
5-pin DIN connector
AT 5-pin DIN
(DIN 41524)
1 CLK

2 DATA
3 N/C
4 GND
5 +5V

1 start bit,
8 data,
1 parity (odd),
1 stop bit
keyboard reset via command string
Supported
5-pin DIN connector
PS/2
"PS/2 port"
6-pin Mini-DIN
(DIN 45322)
1 DATA

2 N/C (or MOUSE DATA)
3 GND
4 +5V
5 CLK
6 N/C (or MOUSE CLK)

1 start bit,
8 data,
1 parity (odd),
1 stop bit
keyboard reset via command string
Supported
6-pin DIN connector
Later
PC compatibles
4-pin USB
Type A connector
1 +5V

2 Data 
3 Data +
4 Ground

sync field plus
8-bit bytes as packets
(HANDSHAKE, TOKEN, DATA, Special packets),
least-significant bit first.
Supported
USB Type A connector

See also

Notes

  1. IBM. IBM Enhanced Keyboard for the Personal Computer Announcement Letter. 1986-04-18 ().
  2. 1 2 Ivens, Kathy (1998). Using Microsoft Windows 95 (4th ed.). Que. p. 165. ISBN 9780789715739.
  3. Mueller, Scott (1998). Upgrading and Repairing PCs. The Scott Mueller library series 1 (10th ed.). Que. p. 450. ISBN 9780789716361.
  4. Corocan, Cate T. (1994-09-05). "Microsoft keyboard ships". InfoWorld. p. 36.
  5. 1 2 3 Mueller, Scott (2011). Upgrading and Repairing PCs (20th ed.). Que. pp. 11151116. ISBN 9780132682183.
  6. 1 2 Xah Lee. "History of Emacs & vi Keys (Keyboard Influence on Keybinding Design)".
  7. Xah Lee. "How To Avoid The Emacs Pinky Problem". Retrieved 2009-11-08.
  8. Edlin, Jim; Bunnell, David (February–March 1982). "IBM's New Personal Computer: Taking the Measure / Part One". PC Magazine. p. 42. Retrieved 20 October 2013.
  9. Edlin, Jim (November 1982). "The PC's Keys". PC Magazine. p. 175. Retrieved 21 October 2013.
  10. Pournelle, Jerry (November 1984). "NCC Reflections". BYTE. p. 361. Retrieved 23 October 2013.
  11. Pournelle, Jerry (June 1983). "Zenith Z-100, Epson QX-10, Software Licensing, and the Software Piracy Problem". BYTE 8 (6). p. 411. Retrieved 20 October 2013.
  12. Williams, Gregg (January 1982). "A Closer Look at the IBM Personal Computer". BYTE. p. 36. Retrieved 19 October 2013.
  13. Curran, Lawrence J., Shuford, Richard S. (November 1983). "IBM's Estridge". BYTE. pp. 88–97. Retrieved 19 March 2016.
  14. Sandler, Corey (January 1983). "Key Tronic's Soft Touch". PC Magazine. p. 347. Retrieved 21 October 2013.
  15. Belkin International. Knowledge Base Article 3532
  16. International Business Machines Corporation (1983): IBM Personal Computer XT Technical Reference Manual, pages D-12 to D-13.
  17. International Business Machines Corporation (1983): IBM Personal Computer XT Technical Reference Manual, pages D-14 to D-15.

External links

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