ASCII Controls


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Michael P. Frank ASCII-controls-v2.2.doc 9/15/06 Page 1 of 9 Discussion of the Intended Meanings of the Nonprintable ASCII Characters Michael P. Frank FAMU-FSU College of Engineering Friday, September 15, 2006 This document discusses how the invisible ASCII characters (that is, the page C0 control characters, codes 0016-1F16, along with the SP (2016) and DEL (7F16) characters) were apparently intended to be used originally, and also something about how they are used in practice presently. This discussion is based loosely on ANSI X3.4-1986, ISO 646-1983, ISO/IEC 6429, and other official standards specifications. However, some of the below material is also a matter of interpretation, or educated guesswork based on experience. The symbol glyphs that I use to graphically represent the control characters in the examples are my own notation, and are not standard. The choice of these characters is explained in a companion document, “A Proposed Set of Mnemonic Symbolic Glyphs for the Visual Representation of C0 Controls and Other Nonprintable ASCII Characters.” The section on transmission control characters needs to be updated to incorporate information from ANSI X3.28-1976, American National Standard for the Use of the Communication Control Characters of American National Standard Code for Information Interchange in Specified Data Communication Links. Likewise, the sections covering the use of the shift in, shift out, and escape characters need to be updated to integrate information from ANSI X3.41-1974, Code Extension Techniques for Use with the 7-Bit Coded Character Set of American National Standard Code for Information Interchange (or equivalently, ISO 2022-1973). 1. Characters Addressed in this Document Table 1 gives the complete list of characters whose meanings are discussed in this document. Table 1. Table of characters discussed in this document. The first column gives the code point in ANSI X3.4’s notation. The next four columns give the hexadecimal, decimal, octal, and binary equivalents. Next is the control sequence that can be used for typing the control character on some systems. Next come a couple of choices of glyphs for visual display of the control character, the first of these being the one intended for this use in the Arial Unicode MS font, the other being my suggestion for a more visually suggestive glyph that is still available in that same font. Next is the official 2-3 character abbreviation for the character name, followed by the official character type. Next is the character type, also represented in the background color of the table row, according to OC=other control (magenta), TC=transmission control (red), FE=format effector (green), CE=code extension (yellow), DC=device control (cyan), IS=information separator (blue). Finally is the section number that addresses that character. x/y Hex Dec Oct Bin Ctl Syms Abbr Name Type Sec 0/0 00 0 000 000 0000 ^@ ␀ ∅ NUL null OC 2.1 0/1 01 1 001 000 0001 ^A ␁ ⌈ SOH start of heading TC 2.2

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