fScan Reference Manual, Chapter 4 (Variables): Contents
fScan supports several different types of internal variables. Values of some variables are global – they do not change when you move from one active window to another. Other variables are workspace or data set specific – their values will change depending on which window is currently active.
In general, data variable values can be accessed by specifying the name of the variable, preceded by the '$' character. To get the status of a variable, substitute '?' for '$'; the status is -1 if the named variable is not defined, it is 0 if it is defined but empty, and it is a positive value (the size of the variable) if it is defined and not empty.