3 col \- column alignment
11 overlays lines to expunge reverse line feeds
13 and half line feeds (ESC-9 and ESC-8)
24 It normally emits only full line feeds;
27 (fine) allows half line feeds too.
30 removes backspaces, printing just one of each pile of overstruck
33 normally converts white space to tabs;
36 overrides this feature.
37 Other escaped characters and non-printing characters are ignored.
41 tbl file | nroff -ms | col | p
42 Format some tables for printing on typewriters;
45 to remove reverse line feeds, and
51 can't back up more than 128 lines or
52 handle more than 800 characters per line,
55 (013) as reverse line feed.