Bit-paired keyboard

In electromechanical systems, this makes a significant difference in ease of implementation, as shifting must be accomplished by some physical linkage.

For this reason, among others (such as ease of collation), the ASCII standard strove to organize the code points so that shifting could be implemented by simply toggling a bit.

This is also present, but less precisely, in the organization of digits and symbols in columns 2 (010) and 3 (011) – this discrepancy is the source of bit-paired layouts.

This could be avoided by changing the key mappings to correspond to the ASCII table, which was notably done in the Teletype Model 33 (1963).

This corresponds in the ASCII table to the following columns (displayed as rows here): There are also less conspicuous differences in the symbol keys: bit-paired and typewriter-paired keyboards agree on <,>.

They died out in the late 1970s, due to the influx of users accustomed to electric typewriters,[citation needed] and were not included in the successor to the X4.14-1971 standard, X4.23-1982.

Other personal computers imitated it,[2] resulting in the typewriter-paired layout becoming standard in the US, and to a lesser extent globally.

In Europe, keyboards of computers for text processing underwent the transition to national typewriter layouts in the late 1970s, but otherwise the international bit-paired layout of ISO 2530 (1975) remained in use until general-purpose PC keyboards replaced the device-specific ones in the late 1980s.