The Input Side: History and Technology of Keyboards

Keyboards are the primary input device for computers, evolving from mechanical typewriters to electronic interfaces. This page explores competing keyboard layouts like QWERTY, Dvorak, and others, their advantages/disadvantages, why QWERTY became standard, how keyboards scan keys, encoding standards like ASCII, IBM PC scan codes, and the shift from parallel to serial protocols (PS/2, USB).

Competing Keyboard Layouts

Keyboard layouts arrange keys for efficient typing. The main competitors are:

QWERTY (1873): Designed by Christopher Sholes for typewriters to prevent jams by separating common letters (e.g., Q-W-E-R-T-Y top row).
Dvorak Simplified Keyboard (1936): Created by August Dvorak and William Dealey; places common letters on home row for efficiency (e.g., A-O-E-U-I top row).
Other Layouts: AZERTY (French), QWERTZ (German); Colemak (2006, modern ergonomic alternative); Workman or Maltron for specialized ergonomics.

Advantages and Disadvantages

Layout	Advantages	Disadvantages
QWERTY	Widely standard; familiar; prevents typewriter jams (historical).	Less efficient (70% typing on top row); higher finger travel; RSI risk.
Dvorak	Ergonomic; 70% home row typing; reduces fatigue; faster for English.	Learning curve; software remapping needed; not standard; less common.
Others (e.g., Colemak)	Balances efficiency/compatibility; ergonomic improvements.	Niche adoption; remapping required; limited hardware support.

Why QWERTY Became the Standard

QWERTY was designed for Remington typewriters in 1873 to slow typists and avoid jams. Its adoption on the Remington No. 2 (1878) spread it widely. By the 1880s, typing schools taught QWERTY, creating inertia. Despite alternatives like Dvorak (faster by 20-40% in studies), switching costs, compatibility, and market dominance (IBM Selectric, PCs) cemented QWERTY. Today, it's universal due to habit and ecosystem lock-in.

How Keyboards Use Scanning on Rows and Columns

Modern keyboards use matrix scanning: keys arranged in a grid (e.g., 8 rows x 16 columns). The controller scans rows sequentially, applying voltage to one row at a time and checking columns for closures (key presses). This detects multiple keys efficiently with fewer wires (e.g., 24 for 104 keys). Debouncing software/hardware filters bounces. Vintage keyboards (e.g., Apple II) used similar matrices but simpler controllers.

Keyboard Standards: ASCII and Others

ASCII (American Standard Code for Information Interchange, 1963) is the dominant 7-bit encoding (128 characters); extended ASCII added 128 more. EBCDIC (IBM, 1964) was used on mainframes. Unicode (1991) superseded for global support. Early teletypes used Baudot (5-bit, 1874). Standards ensure compatibility across devices.

IBM PC Scan Codes

IBM PC keyboards (1981) introduced scan codes: each key press/release sends a code (e.g., 1Eh for 'A' press). The controller generates these, not characters—BIOS/OS maps to ASCII. Set 1 (original) and Set 2 (AT keyboard) evolved for compatibility. This decoupled layout from hardware, enabling remapping (e.g., Dvorak).

From Parallel to Serial Protocols

In the "olden days" (1970s–early 1980s), keyboards used parallel output: multiple wires for data bits (e.g., 8-bit ASCII + strobes). This was simple but cable-heavy. Serial protocols emerged for efficiency:

PS/2 (1987): IBM's bidirectional serial (clock/data lines); 104-key standard; low-cost, but proprietary.
USB (1996): Universal serial bus; plug-and-play, hot-swappable; supports 1,000+ keys/sec; became standard by 2000s.

Serial reduced wires (PS/2: 6 pins; USB: 4) and added features like multimedia keys.

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