predefined variables are commonly used in AutoLISP
Defined as a
string consisting of a double backslash (\\) character. This
variable is used with the command function to pause for user
the constant p (pi). It evaluates to approximately 3.14159.
the constant T. This is used as a
change the value of these variables with the setq function.
However, other applications might rely on their values being
consistent; therefore, it is recommended that you do not modify
these variables. Visual LISP, by default, protects these variables
from redefinition. You can override this protection through the
VLISP Symbol Service feature or by setting a VLISP environment