Six-bit character code
Six-bit character codes were designed for use on computers with word lengths a multiple of 6. Six bits can only encode 64 distinct characters, so these codes generally include only the upper-case letters, the numerals, some punctuation characters, and sometimes control characters. Such codes with additional parity bit were a natural way of storing data on 7-track magnetic tape.
Types of sixbit codes
The earliest computers dealt with numeric data only, and made no provision for character data. Six-bit BCD was used by IBM on early computers such as the IBM 704 in 1954[1]:p.35 . This encoding was replaced by the 8-bit EBCDIC code when System/360 standardized on 8-bit bytes. There are some variants of this type of code (see below).
Six bit character codes generally succeeded the five-bit Baudot code and preceded seven-bit ASCII. One popular variant was DEC SIXBIT. This is simply the ASCII character codes from 32 to 95 coded as 0 to 63 by subtracting 32; it includes the space, punctuation characters, numbers, and uppercase letters, but no control characters. Since it included no control characters, not even end-of-line, it was not used for general text processing. However, six-character names such as filenames and assembler symbols could be stored in a single 36-bit word of PDP-10, and two characters fit in each word of the PDP-1 and PDP-8.
BCD sixbit code
Six-bit BCD code was the adaptation of the punched card code to binary code. IBM applied the terms binary-coded decimal and BCD to the variations of BCD alphamerics used in most early IBM computers, including the IBM 1620, IBM 1400 series, and non-Decimal Architecture members of the IBM 700/7000 series.
COBOL databases sixbit code
A sixbit code was also used in COBOL databases, where end-of-record information was stored separately.[citation needed]
Magnetic stripe card sixbit code
A sixbit code, with added odd parity bit, is used on Track 1 of magnetic stripe cards, as specified in ISO/IEC 7811-2.
Uuencode sixbit code
Uuencode utilizes a sixbit character set for text representation of arbitrary binary data.
DEC sixbit code
A DEC SIXBIT code including a few control characters — along with SO/SI, allowing code extension — was specified as ECMA-1 (see below). Another, less common, variant is obtained by just stripping the high bit of an ASCII code in 32 - 95 range (codes 32 - 63 remain at their positions, higher values have 64 subtracted from them). Such variant was sometimes used on DEC's PDP-8.
Fieldata sixbit code
Fieldata was a six-bit format used by UNIVAC's 1100-series computers. These systems used a 36-bit word (capable of storing 6 Fieldata characters).
Braille sixbit code
Braille characters are represented using six dot positions, arranged in a rectangle. Each position may contain a raised dot or not, so Braille can be considered to be a six-bit binary code.
Examples of BCD sixbit codes
CDC 1604 : Magnetic tape BCD codes
| .0 | .1 | .2 | .3 | .4 | .5 | .6 | .7 | .8 | .9 | .A | .B | .C | .D | .E | .F | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 0 | # | @ | tape mark | |||
| 1. | space | / | S | T | U | V | W | X | Y | Z | record mark | , | % | |||
| 2. | − | J | K | L | M | N | O | P | Q | R | −0 | $ | * | |||
| 3. | & | A | B | C | D | E | F | G | H | I | +0 | . | ¤ | group mark |
CDC 1604 : Punched card codes
| .0 | .1 | .2 | .3 | .4 | .5 | .6 | .7 | .8 | .9 | .A | .B | .C | .D | .E | .F | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 0 | = | − | ||||
| 1. | space | / | S | T | U | V | W | X | Y | Z | , | ( | ||||
| 2. | --- | J | K | L | M | N | O | P | Q | R | −0 | $ | * | |||
| 3. | + | A | B | C | D | E | F | G | H | I | +0 | . | ) |
CDC 1612 printer codes (business applications)
| .0 | .1 | .2 | .3 | .4 | .5 | .6 | .7 | .8 | .9 | .A | .B | .C | .D | .E | .F | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0. | : | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 0 | = | ≠ | ≤ | ! | [ |
| 1. | space | / | S | T | U | V | W | X | Y | Z | ] | , | ( | → | ≡ | ~ |
| 2. | − | J | K | L | M | N | O | P | Q | R | % | $ | * | ↑ | ↓ | > |
| 3. | + | A | B | C | D | E | F | G | H | I | < | . | ) | ≥ | ? | ; |
Examples of sixbit ASCII variants
DEC SIXBIT:
| .0 | .1 | .2 | .3 | .4 | .5 | .6 | .7 | .8 | .9 | .A | .B | .C | .D | .E | .F | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0. | space | ! | " | # | $ | % | & | ' | ( | ) | * | + | , | - | . | / |
| 1. | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | : | ; | < | = | > | ? |
| 2. | @ | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O |
| 3. | P | Q | R | S | T | U | V | W | X | Y | Z | [ | \ | ] | ^ | _ |
ECMA-1:
| .0 | .1 | .2 | .3 | .4 | .5 | .6 | .7 | .8 | .9 | .A | .B | .C | .D | .E | .F | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0. | space | HT | LF | VT | FF | CR | SO | SI | ( | ) | * | + | , | - | . | / |
| 1. | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | : | ; | < | = | > | ? |
| 2. | NULL | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O |
| 3. | P | Q | R | S | T | U | V | W | X | Y | Z | [ | \ | ] | ESC | DEL |
GOST 6-bit code
| _0 | _1 | _2 | _3 | _4 | _5 | _6 | _7 | _8 | _9 | _A | _B | _C | _D | _E | _F | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0_ |
0 00 0 |
1 01 1 |
2 02 2 |
3 03 3 |
4 04 4 |
5 05 5 |
6 06 6 |
7 07 7 |
8 10 8 |
9 11 9 |
+ 12 10 |
- 13 11 |
/ 14 12 |
, 15 13 |
. 16 14 |
SP 17 15 |
| 1_ |
⏨ 20 16 |
↑ 21 17 |
( 22 18 |
) 23 19 |
× 24 20 |
= 25 21 |
; 26 22 |
[ 27 23 |
] 30 24 |
* 31 25 |
‘ 32 26 |
’ 33 27 |
≠ 34 28 |
< 35 29 |
> 36 30 |
|
| 2_ |
А 40 32 |
Б 41 33 |
В 42 34 |
Г 43 35 |
Д 44 36 |
Е 45 37 |
Ж 46 38 |
З 47 39 |
И 50 40 |
Й 51 41 |
К 52 42 |
Л 53 43 |
М 54 44 |
Н 55 45 |
О 56 46 |
П 57 47 |
| 3_ |
Р 60 48 |
С 61 49 |
Т 62 50 |
У 63 51 |
Ф 64 52 |
Х 65 53 |
Ц 66 54 |
Ч 67 55 |
Ш 70 56 |
Щ 71 57 |
Ы 72 58 |
Ь 73 59 |
Э 74 60 |
Ю 75 61 |
Я 76 62 |
DEL 77 63 |
Example of sixbit Braille codes
The following table shows the arrangement of characters, with the hex value, corresponding ASCII character, Braille 6-bit codes (dot combinations), Braille Unicode glyph, and general meaning (the actual meaning may change depending on context).[2][3]
|
|
References
- ↑ IBM Corporation (1954). 704 electronic data-processing machine: manual of operation.
- ↑ "Representing and Displaying Braille". DotlessBraille.org. 2002-02-20. Retrieved 2009-08-09.
- ↑ Halleck, John (2000-08-24). "braille-ascii.ads". Braille.Ascii. Retrieved 2009-08-10.
See also
- Binary-coded decimal
- BCD (character encoding)
- DEC Radix-50
- IBM Transcode
- ASCII
- Baudot code
- EBCDIC
- Unicode
- ANSI X3.64
- UTF-8
- UTF-16
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External links
- Control Data 1604-C Computer. Reference Manual. PDF (7.44 MB)
- ECMA Standard for a 6 Bit Input/Output Character Code PDF (1.53 MB)
- SIXBIT Character Code Reference Digital Equipment Corporation SIXBIT character coding system
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