DESCRIPTION OF THE CLIPPER EXTEND SYSTEM

    Clipper allows you to write functions in other languages and provides
    tools to pass and return parameters to your functions. Your functions
    may then be used like any other function in the Clipper language.  For
    example, you may assign the value returned to a memory variable or
    display it on the screen.

    memvar = MyFunc(<exp>)
    ?  MyFunc(<exp>)

    Clipper's Extend System gives you the ability to access the open
    architecture of the Clipper programming language and makes it possible
    for you to provide for yourself almost any feature or enhancement you
    desire.

    You may write Extend System functions C, or 8086 assembler and link
    them with your compiled application.  The functions in C and Assembler
    can be used to get information which the Clipper language does not have
    access to, such as database file structures or low level information
    available only through DOS interrupts.

    When you create a new user-defined function, you must take care in
    choosing a name that does not to conflict with internal functions or
    their four letter or longer abbreviations.  Your newly named function
    must be used in your code exactly as declared.  No abbreviations are
    permitted at all, so name your user-defined functions exactly as you
    want to use them.

    User-defined functions in C and Assembler, must be used explicitly in
    the application or be declared EXTERNAL at compile time in order for
    them to be included as symbols at link time. {User-defined functions in
    REPORT or LABEL FORMs or in INDEX key expressions must be declared
    EXTERNAL.  For example:

    EXTERNAL MyFunc(), YourFunc()