To make troff (actually a.out):
You will also need to write a driver for your favorite output device.
d202.c provides a model, although it is specialized to a machine no
one has. There are also a variety of postscript drivers that are the
best thing to use if you have a postscript device.
You will also have to make a DESC file for your typesetter and some
font description files; see dev202 for examples. These describe the
named characters, widths, kerning information, and output codes.
Nroff is the same program as troff, so you should
cp a.out /usr/bin/troff
ln /usr/bin/troff /usr/bin/nroff
or the equivalent.
You will also need terminal description files for your terminals; see
tab.37, tab.450 and tab.lp for examples.
Troff uses files that are normally stored in /usr/lib/font;
macro packages are in /usr/lib/tmac; and nroff tables are in
/usr/lib/term. You can edit tdef.h to change these assumptions.
There have been a few features since the last version, and a number of
significant internal changes. Not all are improvements, of course.
Most of the more recent changes, including bug fixes, are in FIXES,
which you should read also.