Six-bit character code

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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[edit]

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[edit]

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[edit]

A sixbit code was also used in COBOL databases, where end-of-record information was stored separately.[citation needed]

Magnetic stripe card sixbit code[edit]

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[edit]

Uuencode utilizes a sixbit character set for text representation of arbitrary binary data.

DEC sixbit code[edit]

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[edit]

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[edit]

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[edit]

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[edit]

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[edit]

_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

37
31
 
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[edit]

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]

Hex ASCII Glyph Braille Dots Braille Glyph Braille Meaning
20 (space) ⠀ (braille pattern blank) (space)
21 ! 2-3-4-6 ⠮ (braille pattern dots-2346) the
22 " 5 ⠐ (braille pattern dots-5) (contraction)
23 # 3-4-5-6 ⠼ (braille pattern dots-3456) (number prefix)
24 $ 1-2-4-6 ⠫ (braille pattern dots-1246) ed
25 % 1-4-6 ⠩ (braille pattern dots-146) sh
26 & 1-2-3-4-6 ⠯ (braille pattern dots-12346) and
27 ' 3 ⠄ (braille pattern dots-3) '
28 ( 1-2-3-5-6 ⠷ (braille pattern dots-12356) of
29 ) 2-3-4-5-6 ⠾ (braille pattern dots-23456) with
2A * 1-6 ⠡ (braille pattern dots-16) ch
2B + 3-4-6 ⠬ (braille pattern dots-346) ing
2C , 6 ⠠ (braille pattern dots-6) (uppercase prefix)
2D - 3-6 ⠤ (braille pattern dots-36) -
2E . 4-6 ⠨ (braille pattern dots-46) (italic prefix)
2F / 3-4 ⠌ (braille pattern dots-34) st
30 0 3-5-6 ⠴ (braille pattern dots-356) "
31 1 2 ⠂ (braille pattern dots-2) ,
32 2 2-3 ⠆ (braille pattern dots-23) ;
33 3 2-5 ⠒ (braille pattern dots-25) :
34 4 2-5-6 ⠲ (braille pattern dots-256) .
35 5 2-6 ⠢ (braille pattern dots-26) en
36 6 2-3-5 ⠖ (braille pattern dots-235) !
37 7 2-3-5-6 ⠶ (braille pattern dots-2356) ( or )
38 8 2-3-6 ⠦ (braille pattern dots-236) " or ?
39 9 3-5 ⠔ (braille pattern dots-35) in
3A : 1-5-6 ⠱ (braille pattern dots-156) wh
3B ; 5-6 ⠰ (braille pattern dots-56) (letter prefix)
3C < 1-2-6 ⠣ (braille pattern dots-126) gh
3D = 1-2-3-4-5-6 ⠿ (braille pattern dots-123456) for
3E > 3-4-5 ⠜ (braille pattern dots-345) ar
3F ? 1-4-5-6 ⠹ (braille pattern dots-1456) th
 
Hex ASCII Glyph Braille Dots Braille Glyph Braille Meaning
40 @ 4 ⠈ (braille pattern dots-4) (accent prefix)
41 A 1 ⠁ (braille pattern dots-1) a
42 B 1-2 ⠃ (braille pattern dots-12) b
43 C 1-4 ⠉ (braille pattern dots-14) c
44 D 1-4-5 ⠙ (braille pattern dots-145) d
45 E 1-5 ⠑ (braille pattern dots-15) e
46 F 1-2-4 ⠋ (braille pattern dots-124) f
47 G 1-2-4-5 ⠛ (braille pattern dots-1245) g
48 H 1-2-5 ⠓ (braille pattern dots-125) h
49 I 2-4 ⠊ (braille pattern dots-24) i
4A J 2-4-5 ⠚ (braille pattern dots-245) j
4B K 1-3 ⠅ (braille pattern dots-13) k
4C L 1-2-3 ⠇ (braille pattern dots-123) l
4D M 1-3-4 ⠍ (braille pattern dots-134) m
4E N 1-3-4-5 ⠝ (braille pattern dots-1345) n
4F O 1-3-5 ⠕ (braille pattern dots-135) o
50 P 1-2-3-4 ⠏ (braille pattern dots-1234) p
51 Q 1-2-3-4-5 ⠟ (braille pattern dots-12345) q
52 R 1-2-3-5 ⠗ (braille pattern dots-1235) r
53 S 2-3-4 ⠎ (braille pattern dots-234) s
54 T 2-3-4-5 ⠞ (braille pattern dots-2345) t
55 U 1-3-6 ⠥ (braille pattern dots-136) u
56 V 1-2-3-6 ⠧ (braille pattern dots-1236) v
57 W 2-4-5-6 ⠺ (braille pattern dots-2456) w
58 X 1-3-4-6 ⠭ (braille pattern dots-1346) x
59 Y 1-3-4-5-6 ⠽ (braille pattern dots-13456) y
5A Z 1-3-5-6 ⠵ (braille pattern dots-1356) z
5B [ 2-4-6 ⠪ (braille pattern dots-246) ow
5C \ 1-2-5-6 ⠳ (braille pattern dots-1256) ou
5D ] 1-2-4-5-6 ⠻ (braille pattern dots-12456) er
5E ^ 4-5 ⠘ (braille pattern dots-45) (contraction)
5F _ 4-5-6 ⠸ (braille pattern dots-456) (contraction)

References[edit]

  1. ^ IBM Corporation (1954). 704 electronic data-processing machine: manual of operation. 
  2. ^ "Representing and Displaying Braille". DotlessBraille.org. 2002-02-20. Retrieved 2009-08-09. 
  3. ^ Halleck, John (2000-08-24). "braille-ascii.ads". Braille.Ascii. Retrieved 2009-08-10. 

See also[edit]

External links[edit]