FUNCTION               Declaring and Using a Function                pp 137

 Syntax:  Function Name (Formal Parm List) : Type ;

 Type:    Scalar, String, or Pointer

 Form:    Declaration

 Purpose: A function defines a subroutine.  It may be either pre-declared
          as a part of the TURBO system, or user declared as defined by
          the programmer.  The intent of a function is to return a result.

          The reserved word 'Function' is followed by an identifer which
          becomes the name of the function, optionally followed by a
          list of formal parameters.  Type identifies the returned result.

          All identifiers in the formal parameter list and the declaration
          part of the function are local to the function.
          These identifiers are not visible outside the function.
          This is termed the scope of the identifier.

 Parms:   The formal parameters are used to define the function.  The
          names assigned to them are only identifiers, not actual variables.
          The formal parameters only identify the number and type of
          variables that will be used by the function.


          Define:  Function SQUARE (NumVar) : Real ;
          Usage:   Number := SQUARE (200) ;

          This example indicates to the compiler that when SQUARE is called
          it will be called with one parameter of type Real.


 Types:   Formal parameters can be of two types:  Value or Variable.
          Value parameters are constants or actual values of variables.
          The SQUARE function uses Value parameters in the example.
          A constant is passed as a value parameter when the above
          function is called.


          Variable parameters are the actual addresses of the variables.
          The variables passed when the function is called will be
          acted upon by the function.

          Define:  Function SQUARE (VAR Dummy1 : Integer) : Real ;
                   Begin
                   Dummy1 := Dummy1 * Dummy1 { Square the number }
                   End;

          Usage:   Squared_Number := SQUARE (IntVar) ;

          Dummy1 is a Variable formal parameter.  It indicates to the
          compiler that when SQUARE is called, the parm passed with the
          function will be the actual variable address.
          The variable will then be acted upon by the function.