Submitter: UK C Panel
Submission Date: 2001-09-07
Source: Clive D.W. Feather <email@example.com>
Subject: graphic characters
The Standard uses the terms "printing character", "graphic character", and "nongraphic character". The first is discussed in 5.2.2#1 and defined formally in 7.4#3:
[#3] The term printing character refers to a member of a locale-specific set of characters, each of which occupies one printing position on a display device;
A "nongraphic character" is clearly a character which is not a graphic character, but "graphic character" is nowhere defined. It is used only in 5.2.1#3, which requires "the following 29 graphic characters" to be part of the basic character sets, while "nongraphic character" is used in 5.2.2#2 and 126.96.36.199#8 when discussing the \a \b \f \n \r \t and \v escape sequences.
The key questions are:
In addition, given that the seven characters corresponding to the escape sequences above are required to be control characters (see 5.2.1#3):
I believe that the answers should be:
However, it is not clear that these answers can be derived from the Standard (though if (1) and (2) are "yes", (3) must at least be "yes in the C locale").
Suggested Technical Corrigendum
To address (1): in 5.2.1#3, replace "29 graphic characters" with "29 printing characters".
To address (4): in 5.2.2#2 and 188.8.131.52#8 replace "nongraphic" with "control".
To address (2): append to 5.2.1#4:
A graphical mark character is one of the 29 other printing characters listed above.in 184.108.40.206#2, insert between the two sentences:
The isalpha function returns false for all graphical mark characters.and in 220.127.116.11#2, change "characters for which" to "characters which are not graphical mark characters and for which".
Given the above changes, (3) can be derived from the modified Standard.
The referenced sections in the standard only use the term "non-graphic character" in the context of backslash-escape sequences, for which the standard is clear enough, and no changes are needed.
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