FRE Function Details
 
Syntax
  FRE(stringexpression)
  FRE(numeric-expression)
 
The FRE function returns the following values when it has a numeric
argument (numeric-expression):
 
  Argument        Value Returned
  -1              The size, in bytes, of the largest nonstring
                  array that could be dimensioned
  -2              The amount, in bytes, of unused stack space
                  available to the program
  Any other       The size of the next free block of string
  numeric value   storage
 
When the argument is a string expression (stringexpression), FRE returns the
size, in bytes, of the free string storage. Before FRE returns the number of
free bytes, it compacts the free string storage into a single block.
 
  Note: FRE(-2) returns meaningful values only when a program is
        executing. Values returned by FRE(-2) are not accurate when
        the function is called from the Immediate window, during
        program tracing, or when watching a variable.