Varicode

Varicode is a Huffman code for use in PSK31. It supports all ASCII characters, but the characters used most frequently in English have shorter codes. The space between characters is indicated by a 00 sequence, a variation of Fibonacci coding. Originally created for speeding up real-time keyboard-to-keyboard exchanges over low bandwidth links, it is a very useful format to shrink text files. Varicode is freely available.^[1][2][3]

Limitations

• Varicode provides somewhat weaker compression in languages other than English that use same characters as in English.

Varicode table

Control characters

Varicode	Oct	Dec	Hex	Abbr	Description
1010101011	000	0	00	NUL	Null character
1011011011	001	1	01	SOH	Start of Header
1011101101	002	2	02	STX	Start of Text
1101110111	003	3	03	ETX	End of Text
1011101011	004	4	04	EOT	End of Transmission
1101011111	005	5	05	ENQ	Enquiry
1011101111	006	6	06	ACK	Acknowledgment
1011111101	007	7	07	BEL	Bell
1011111111	010	8	08	BS	Backspace
11101111	011	9	09	HT	Horizontal Tab
11101	012	10	0A	LF	Line feed
1101101111	013	11	0B	VT	Vertical Tab
1011011101	014	12	0C	FF	Form feed
11111	015	13	0D	CR	Carriage return
1101110101	016	14	0E	SO	Shift Out
1110101011	017	15	0F	SI	Shift In
1011110111	020	16	10	DLE	Data Link Escape
1011110101	021	17	11	DC1	Device Control 1 (XON)
1110101101	022	18	12	DC2	Device Control 2
1110101111	023	19	13	DC3	Device Control 3 (XOFF)
1101011011	024	20	14	DC4	Device Control 4
1101101011	025	21	15	NAK	Negative Acknowledgement
1101101101	026	22	16	SYN	Synchronous Idle
1101010111	027	23	17	ETB	End of Trans. Block
1101111011	030	24	18	CAN	Cancel
1101111101	031	25	19	EM	End of Medium
1110110111	032	26	1A	SUB	Substitute
1101010101	033	27	1B	ESC	Escape
1101011101	034	28	1C	FS	File Separator
1110111011	035	29	1D	GS	Group Separator
1011111011	036	30	1E	RS	Record Separator
1101111111	037	31	1F	US	Unit Separator
1110110101	177	127	7F	DEL	Delete

Printable characters

Varicode Oct Dec Hex Glyph 1 040 32 20 SP 111111111 041 33 21 ! 101011111 042 34 22 " 111110101 043 35 23 # 111011011 044 36 24 $ 1011010101 045 37 25 % 1010111011 046 38 26 & 101111111 047 39 27 ' 11111011 050 40 28 ( 11110111 051 41 29 ) 101101111 052 42 2A * 111011111 053 43 2B + 1110101 054 44 2C , 110101 055 45 2D - 1010111 056 46 2E . 110101111 057 47 2F / 10110111 060 48 30 0 10111101 061 49 31 1 11101101 062 50 32 2 11111111 063 51 33 3 101110111 064 52 34 4 101011011 065 53 35 5 101101011 066 54 36 6 110101101 067 55 37 7 110101011 070 56 38 8 110110111 071 57 39 9 11110101 072 58 3A : 110111101 073 59 3B ; 111101101 074 60 3C < 1010101 075 61 3D = 111010111 076 62 3E > 1010101111 077 63 3F ?

Varicode Oct Dec Hex Glyph 1010111101 100 64 40 @ 1111101 101 65 41 A 11101011 102 66 42 B 10101101 103 67 43 C 10110101 104 68 44 D 1110111 105 69 45 E 11011011 106 70 46 F 11111101 107 71 47 G 101010101 110 72 48 H 1111111 111 73 49 I 111111101 112 74 4A J 101111101 113 75 4B K 11010111 114 76 4C L 10111011 115 77 4D M 11011101 116 78 4E N 10101011 117 79 4F O 11010101 120 80 50 P 111011101 121 81 51 Q 10101111 122 82 52 R 1101111 123 83 53 S 1101101 124 84 54 T 101010111 125 85 55 U 110110101 126 86 56 V 101011101 127 87 57 W 101110101 130 88 58 X 101111011 131 89 59 Y 1010101101 132 90 5A Z 111110111 133 91 5B [ 111101111 134 92 5C \ 111111011 135 93 5D ] 1010111111 136 94 5E ^ 101101101 137 95 5F _

Varicode Oct Dec Hex Glyph 1011011111 140 96 60 ` 1011 141 97 61 a 1011111 142 98 62 b 101111 143 99 63 c 101101 144 100 64 d 11 145 101 65 e 111101 146 102 66 f 1011011 147 103 67 g 101011 150 104 68 h 1101 151 105 69 i 111101011 152 106 6A j 10111111 153 107 6B k 11011 154 108 6C l 111011 155 109 6D m 1111 156 110 6E n 111 157 111 6F o 111111 160 112 70 p 110111111 161 113 71 q 10101 162 114 72 r 10111 163 115 73 s 101 164 116 74 t 110111 165 117 75 u 1111011 166 118 76 v 1101011 167 119 77 w 11011111 170 120 78 x 1011101 171 121 79 y 111010101 172 122 7A z 1010110111 173 123 7B { 110111011 174 124 7C | 1010110101 175 125 7D } 1011010111 176 126 7E ~

Character lengths

Beginning with the single-bit code "1", valid varicode values may be formed by prepending a "1" or "10" to a shorter code. Thus, the number of codes of length n is equal to the Fibonacci number F_n. Varicode uses the 88 values of lengths up to 9 bits, and 40 of the 55 codes of length 10.

As transmitted, the codes are two bits longer due to the trailing delimiter 00.

ASCII characters by varicode length

Bits	Codes	Characters
1	1	SP
2	1	e
3	2	o t
4	3	a i n
5	5	LF CR l r s
6	8	- c d f h m p u
7	13	, . = A E I S T b g v w y
8	21	HT ( ) 0 1 2 3 : B C D F G L M N O P R k x
9	34	! " # $ ' * + / 4 5 6 7 8 9 ; < > H J K Q U V W X Y [ \ ] _ j q z |
10	40	NUL SOH STX ETX EOT ENQ ACK BEL BS VT FF SO SI DLE DC1 DC2 DC3 DC4 NAK SYN ETB CAN EOM SUB ESC FS GS RS US % & ? @ Z ^ ` { } ~ DEL

References

1. Steven L Karty, N5SK. "PSK31 Spec". ARRL Website. Retrieved 18 Dec 2010.
2. Peter Martinez, G3PLX. "PSK31: A new radio-teletype mode with a traditional philosophy" (PDF). Retrieved 18 Dec 2010.
3. ITU Working Party 5A. "ITU-R M.2034: Telegraphic Alphabet for Data Communication by Phase Shift Keying at 31 Baud in the Amateur and Amateur-Satellite Services.". International Telecommunication Union (approved Feb, 2013). Retrieved 21 Feb 2013.