Reference sheets · 1969
ASCII: USA Standard Code for Information Interchange
Reference sheet · RFC 20 · USAS X3.4-1968
- Source
- rfc-editor.org
- Retrieved
- 27 September 2026
- License
- MIT (compilation); data: RFC 20 (USAS X3.4-1968)
- Rights holder
- vodhash, 2026 (compilation); RFC 20: Vint Cerf, 1969
- Language
- English
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction [...] (MIT License of this repository, LICENSE)
About this edition and its rights
Edition
RFC Editor plain-text edition of RFC 20 (put into machine readable form by Robbie Bennet in September 1999), sections 2 (Standard Code) and 4 (Legend). The 128 positions of the code table, the control abbreviations and names of legend 4.1 and the graphic names of legend 4.2, with their group marks (CC), (FE) and (IS) and their note numbers, were extracted by script from that file. The decimal and hexadecimal values are computed from the column and row of each position (16 times the column plus the row), as section 3 defines them. In each cell the group mark is set as a tag after the name, the note numbers as a superscript, and the alternative names in parentheses in italic. The legend’s “File Separator IS)” is set as “File Separator (IS)”. Letters and digits have no name in the legend and get none. The notes, the explanation of the table and the lists of groups were written for this sheet from sections 1, 3, 4, 5 and 6 of RFC 20; the Internet Standard status comes from the RFC Editor’s page https://www.rfc-editor.org/info/rfc20 (STD 80).
Rights
License notice: “Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction [...] (MIT License of this repository, LICENSE)”
The sheet follows RFC 20, https://www.rfc-editor.org/rfc/rfc20.txt, which carries no copyright notice and no distribution statement; the code values and names are facts of the standard. RFC Editor FAQ (https://www.rfc-editor.org/faq/): “All RFCs may be freely reproduced and translated (unmodified).” IETF Trust FAQ (https://trustee.ietf.org/about/faq/): “Since the beginning of the RFC series, reproduction of whole RFCs (including translation into a language other than English) has been allowed and encouraged. The IETF Trust and the RFC Editor place no restrictions on this.”, and on RFCs that predate the IETF: “numerous RFCs were published prior to the existence of the IETF (i.e. prior to January 1986). The IETF Trust cannot offer definitive advice in these cases.” For extracts, the same FAQ says that “the IETF Trust will tolerate fair use of other extracts, but you must indicate the source of the extract”: the footer names RFC 20 and its URL. The names of the legend are the only words taken from the RFC.
The code#
RFC 20, ASCII format for Network Interchange, written by Vint Cerf at UCLA and dated 16 October 1969, proposes standard 7-bit ASCII in an 8-bit byte whose high-order bit is always 0, for the HOST-HOST connections of the network. It attaches the code of the USA Standard Code for Information Interchange, USAS X3.4-1968, whose table is set above with the names of its legend. The RFC Editor lists RFC 20 as Internet Standard STD 80.
Reading the table#
A character is a number of seven bits, b7 the high-order bit and b1 the low-order bit. Bits b7, b6 and b5 give the column, 0 to 7, and bits b4 to b1 the row, 0 to 15, so that the standard can name a position as column/row: K is at 4/11, bits 1001011. Each cell gives the code in decimal, 16 times the column plus the row, and in hexadecimal, whose two digits are the column and the row. Letters and digits have no name in the legend.
The standard defines the order of any two characters, for collation, by their binary values, and prescribes no type style for the graphics.
Control characters#
Columns 0 and 1 hold 32 control characters, shown by their abbreviations. The legend marks three groups:
- CC, communication control: SOH, STX, ETX, EOT, ENQ, ACK, DLE, NAK, SYN and ETB.
- FE, format effector: BS, HT, LF, VT, FF and CR.
- IS, information separator: FS, GS, RS and US, from the most inclusive, FS, to the least, US.
SP, the space at 2/0, is a graphic character, normally non-printing, and DEL, at 7/15, is not a control character in the strict sense.
Notes of the legend#
Small figures in the table refer to the notes of the legend of RFC 20:
- DEL is not a control character in the strict sense.
- The symbols at 2/2, 2/7, 2/12, 5/14, 6/0 and 7/14 can also serve as diacritical marks, as Appendix A of the standard describes; RFC 20 does not reproduce its appendixes.
- These characters should not be used in international interchange without agreement between sender and recipient.
- Where the number sign is not needed, the pound sterling symbol may take position 2/3.