5.3.1 Motion Quanta

The basic unit u is not necessarily an output device’s smallest addressable length; u can be smaller to avoid integer rounding errors. The minimum distances that a device can work with in the horizontal and vertical directions are termed its motion quanta. The formatter rounds measurements to applicable motion quanta. Half-quantum fractions round toward zero.

Register: \n[.H]

Register: \n[.V]

These read-only registers interpolate the horizontal and vertical motion quantum, respectively, of the output device in basic units.

For example, we might draw short baseline rules on a terminal device as follows. See Drawing Geometric Objects.

.tm \n[.H]
    error→ 24
.nf
\l'36u' 36u
\l'37u' 37u
    ⇒ _ 36u
    ⇒ __ 37u