PS TEXT FORMAT Reference Manual

Expressions
11387 Tandem Computers Incorporated 5-5
Variables A variable is a name that represents a value. You create your variables and
assign it a value. The name must begin with a letter; the remaining
characters may be letters, numbers, and/or underscore (_) characters. A
variable name is restricted to 32 characters; if TFORM finds a name longer
than that, it issues an error message. You can use variable names that are
as short as you like, but it’s advisable to use enough characters to make the
names meaningful. For example, FIRST_NAME is much more descriptive
than FN, especially if a long time has passed since you last looked at it.
You use the ASSIGN, FILE READ, or LEVEL REFERENCE command to
assign a value to your variable (these commands are described in Section
3). A variable with no value has no inherent type (numeric or string), but
once you assign it a value, it assumes the type of that value and becomes
subject to the usage rules for that type. If you later assign another value to
the variable, it assumes the type of that value.
System Variables In addition to the variables you create, TFORM maintains a set of system
variables that you can refer to and use in expressions; you cannot,
however, assign values directly to them—TFORM assigns appropriate
values when you use these variables.
System variables keep track of such things as the current page number, the
input-file line number being processed, the sizes of the margins, the current
tab stop settings, the current section title, today’s date, and the time (down
to the second) at which the formatting run began. TFORM stores other
data in system variables as well, such as line height; line width; items
defined by DEFINE, PRINT, and SET commands; and file information.
All of the names of TFORM-maintained variables begin with “SYS_” ; don’t
use the prefix SYS_ in the name of any of the variables you create.
The following are descriptions of all the system variables. The designations
(N) and (S) indicate whether a given variable is of numeric or string type.
SYS_BOTTOMMARGIN TFORM stores in this variable the number of decipoints between the last
footer and the bottom of the form. (N)