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gtroff
(like many other programs) requires numeric parameters to
specify various measurements. Most numeric parameters^{9} 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
See Fractional Type Sizes, for a discussion of these units.
f
Fractions. Value is 65536. See 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. See Sizes, for more information about this.
M
100ths of an em.
• Default Units: |
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