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A numeric character reference refers to a character by its Universal Character Set/Unicode code point, and a character entity reference refers to a character by a predefined name. A numeric character reference uses the format &#nnnn; or &#xhhhh; where nnnn is the code point in decimal form, and hhhh is the code point in hexadecimal form.
ASCII was incorporated into the Unicode (1991) character set as the first 128 symbols, so the 7-bit ASCII characters have the same numeric codes in both sets. This allows UTF-8 to be backward compatible with 7-bit ASCII, as a UTF-8 file containing only ASCII characters is identical to an ASCII file containing the same sequence of characters.
A user may define custom functions which, like variables, are identified by name rather than by a non-textual symbol. The function header defines whether a custom function is niladic (no arguments), monadic (one right argument) or dyadic (left and right arguments), the local name of the result (to the left of the ← assign arrow), and whether ...
A code point is a value or position of a character in a coded character set. [10] A code space is the range of numerical values spanned by a coded character set. [10] [12] A code unit is the minimum bit combination that can represent a character in a character encoding (in computer science terms, it is the word size of the character encoding).
Caret notation is a notation for control characters in ASCII. The notation assigns ^A to control-code 1, sequentially through the alphabet to ^Z assigned to control-code 26 (0x1A). For the control-codes outside of the range 1–26, the notation extends to the adjacent, non-alphabetic ASCII characters.
The hardware code page of the original IBM PC supplied the following box-drawing characters, in what DOS now calls code page 437. This subset of the Unicode box-drawing characters is thus included in WGL4 and is far more popular and likely to be rendered correctly:
For example, the key labelled "Backspace" typically produces code 8, "Tab" code 9, "Enter" or "Return" code 13 (though some keyboards might produce code 10 for "Enter"). Many keyboards include keys that do not correspond to any ASCII printable or control character, for example cursor control arrows and word processing functions.
In many programming languages, the vertical bar is used to designate the logic operation or, either bitwise or or logical or. Specifically, in C and other languages following C syntax conventions, such as C++, Perl, Java and C#, a | b denotes a bitwise or; whereas a double vertical bar a || b denotes a (short-circuited) logical or.