Hyphen-minus facts for kids
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Hyphen-minus
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The hyphen-minus (-) is a character used in digital documents and computing to represent a hyphen (‐) or a minus sign (−).
Description
The use of a single character for both hyphen and minus was a compromise made in the early days of fixed-width typewriters and computer displays. However, in proper typesetting and graphic design, there are distinct characters for hyphens, dashes, and the minus sign. Usage of the hyphen-minus nonetheless persists in many contexts, as it is well-known, easy to enter on keyboards, and in the same location in all common character sets.
As the minus sign
Most programming languages, restricting themselves to 7-bit ASCII, use the hyphen-minus, rather than the Unicode character for denoting subtraction and negative numbers.
The minus sign is nominally the same width as the plus sign. In proportional typefaces it is longer than a hyphen. During typesetting a word wrap may also occur following a hyphen-minus, unlike the minus sign proper which is treated as a mathematical symbol. These differences make "-" as a substitute for minus signs undesirable in professional typography.
Command line
The ASCII hyphen-minus character is also often used when specifying command-line options. The character is usually followed by one or more letters that indicate specific actions. Various implementations of the getopt function to parse command-line options additionally allow the use of two hyphen-minus characters ( -- ) to specify long option names that are more descriptive than their single-letter equivalents. Another use of hyphens is that employed by programs written with pipelining in mind: a single hyphen may be recognized in lieu of a filename, with the hyphen then serving as an indicator that a standard stream, instead of a file, is to be worked with.
Other uses
On typewriters, it was conventional to use a pair of hyphens to represent an em dash, and this convention is still sometimes used in computer text.
The hyphen-minus is often used to represent an en dash, which may be used to indicate ranges (such as a time range of "2000–2004"), direction (as in "The Los Angeles–London flight"), and other cases of connection. The en dash is normally longer (the width of a letter "n") than a hyphen. The hyphen connects closely, the en dash less closely, while the em dash—with the width (at least traditionally) of the capital letter "M"—separates.
In some programming languages -- marks beginning of a comment. Likewise, it can occasionally start the signature block.
