4.  Indents and Line Lengths

      troff starts with a line length of 6.5 inches, too wide for 8½×11 paper. To reset the line length, use the .llcommand, as in ^ll 6i
As with
.spthe actual length can be specified in several ways;
inches are probably the most intuitive.

      The maximum line length provided by the typesetter is 7.5 inches, by the way. To use the full width, you will have to reset the default physical left margin (``page offset''), which is normally slightly less than one inch from the left edge of the paper. This is done by the .pocommand. ^po 0
sets the offset as far to the left as it will go.

      The indent command .incauses the left margin to be indented by some specified amount from the page offset. If we use .into move the left margin in, and .llto move the right margin to the left, we can make offset blocks of text: ^in 0.3i
^ll -0.3i
text to be set into a block
^ll +0.3i
^in -0.3i
will create a block that looks like this:
Pater noster qui est in caelis sanctificetur nomen tuum; adveniat regnum tuum; fiat voluntas tua, sicut in caelo, et in terra. ... Amen. Notice the use of `+' and `-' to specify the amount of change. These change the previous setting by the specified amount, rather than just overriding it. The distinction is quite important: .ll +1imakes lines one inch longer; .ll 1imakes them one inch long.

      With .in.lland .pothe previous value is used if no argument is specified.

      To indent a single line, use the `temporary indent' command .tiFor example, all paragraphs in this memo effectively begin with the command ^ti 3
Three of what?
The default unit for
.tias for most horizontally oriented commands
(.ll.in.pois ems;
an em is roughly the width of the letter `m'
in the current point size.
(Precisely, a em in size
p
is
p
points.)
Although inches are usually clearer than ems to people who don't set type
for a living,
ems have a place:
they are a measure of size that is proportional to the current point size.
If you want to make text that keeps its proportions
regardless of point size,
you should use ems for all dimensions.
Ems can be specified as scale factors directly,
as in
.ti 2.5m

      Lines can also be indented negatively if the indent is already positive: ^ti -0.3i
causes the next line to be moved back three tenths of an inch.
Thus to make a decorative initial capital,
we indent the whole paragraph, then move the letter `P' back with
a
.ticommand:

Pater noster qui est in caelis sanctificetur nomen tuum; adveniat regnum tuum; fiat voluntas tua, sicut in caelo, et in terra. ... Amen. Of course, there is also some trickery to make the `P' bigger (just a `\s36P\s0'), and to move it down from its normal position (see the section on local motions).