User`s guide

In general, most of the following system parameters have one
operator for determining current status of the system parameter.
The second operator sets the parameter to the specified value or
state. Each operator is examined in the following section.
Syntax Key
Varying fonts and placement of words in the syntax examples have
distinct meanings. PostScript operators are presented in Italic Bold
to indicate this word is actually typed in from the keyboard.
Regular bold is used for data values, such as booleans, integers,
or strings.
Data values of integers, booleans and strings are either entered by
you through the keyboard or they are internally returned by
PostScript. You enter the value when its placement in the syntax is
shown before the PostScript operator. If it is shown in the syntax
after the PostScript operator, you do not enter any value; PostScript
returns the value.
Chapter 10
PostScript: Operator Dictionary 10-7