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5.3 Measurements
================

The formatter sometimes requires the input of numeric parameters to
specify measurements.  These are specified as integers or decimal
fractions with an optional "scaling unit" suffixed.  A scaling unit is a
letter that immediately follows the last digit of a number.  Digits
after the decimal point are optional.  Measurement expressions include
'10.5p', '11i', and '3.c'.

   Measurements are scaled by the scaling unit and stored internally
(with any fractional part discarded) in basic units.  The device
resolution can therefore be obtained by storing a value of '1i' to a
register.  The only constraint on the basic unit is that it is at least
as small as any other unit.

'u'
     Basic unit.

'i'
     Inch; defined as 2.54 centimeters.

'c'
     Centimeter; a centimeter is about 0.3937 inches.

'p'
     Point; a typesetter's unit used for measuring type size.  There are
     72 points to an inch.

'P'
     Pica; another typesetter's unit.  There are 6 picas to an inch and
     12 points to a pica.

's'
'z'
     *Note Using Fractional Type Sizes::, for a discussion of these
     units.

'f'
     GNU 'troff' defines this unit to scale decimal fractions in the
     interval [0, 1] to 16-bit unsigned integers.  It multiplies a
     quantity by 65,536.  *Note Colors::, for usage.

   The magnitudes of other scaling units depend on the text formatting
parameters in effect.  These are useful when specifying measurements
that need to scale with the typeface or vertical spacing.

'm'
     Em; an em is equal to the current type size in points.  It is named
     thus because it is approximately the width of the letter 'M'.

'n'
     En; an en is one-half em.

'v'
     Vee; recall *note Page Geometry::.

'M'
     Hundredth of an em.

* Menu:

* Motion Quanta::
* Default Units::