groff: Measurements
5.2 Measurements
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'gtroff' (like many other programs) requires numeric parameters to
specify various measurements. Most numeric parameters(1) (
Measurements-Footnote-1) may have a "measurement unit" attached.
These units are specified as a single character that immediately follows
the number or expression. Each of these units are understood, by
'gtroff', to be a multiple of its "basic unit". So, whenever a
different measurement unit is specified 'gtroff' converts this into its
"basic units". This basic unit, represented by a 'u', is a device
dependent measurement, which is quite small, ranging from 1/75th to
1/72000th of an inch. The values may be given as fractional numbers;
however, fractional basic units are always rounded to integers.
Some of the measurement units are completely independent of any of
the current settings (e.g. type size) of 'gtroff'.
'i'
Inches. An antiquated measurement unit still in use in certain
backwards countries with incredibly low-cost computer equipment.
One inch is equal to 2.54cm.
'c'
Centimeters. One centimeter is equal to 0.3937in.
'p'
Points. This is a typesetter's measurement used for measure type
size. It is 72 points to an inch.
'P'
Pica. Another typesetting measurement. 6 Picas to an inch (and
12 points to a pica).
's'
'z'
Fractional Type Sizes, for a discussion of these units.
'f'
Fractions. Value is 65536. Colors, for usage.
The other measurements understood by 'gtroff' depend on settings
currently in effect in 'gtroff'. These are very useful for specifying
measurements that should look proper with any size of text.
'm'
Ems. This unit is equal to the current font size in points. So
called because it is _approximately_ the width of the letter 'm' in
the current font.
'n'
Ens. In 'groff', this is half of an em.
'v'
Vertical space. This is equivalent to the current line spacing.
Sizes, for more information about this.
'M'
100ths of an em.
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