PS TEXT FORMAT Reference Manual

4 Escape Sequences
11387 Tandem Computers Incorporated 4-1
A trigger character in the first position of an input line signals the presence
of a command line. If TFORM sees a trigger character elsewhere in a line, it
expects to find an escape sequence (although an escape sequence can occur
at the beginning of a line as well). TFORM can tell by the context whether
the entity following a trigger is indeed an escape sequence or something
else, such as a comment. “Escape sequence” is an historical term, arising
from the fact that the ESCape character (ASCII code 27) was sometimes
used to signal such entities.
This section describes the TFORM escape sequences. They are used to
define formatting metacharacters, rendition controls, and indirection
escape sequences (also known as value substitutions).
Note In the following illustration of rendition control and indirection escape sequences, spaces
have been added for easier reading. However, TFORM will view these spaces as actual
characters when it processes a file, so add spaces with care.
Metacharacters A trigger followed by one of these single nonalphabetic characters
(! - # . < > & or =) is called a metacharacter; when embedded in your text,
a metacharacter tells TFORM to perform a special formatting activity.
TFORM normally does not print metacharacters. If you want TFORM to
print a metacharacter you must insert a second trigger character in front of
the metacharacter. These two trigger characters, called a literal trigger
metacharacter, specifies that the trigger character is to be printed as text.
Metacharacters control such formatting activities as tabulation,
backspacing, and mandatory blanks and returns.