The Open service makes an existing file available for processing
    by your program. The Open service specifies the type of record
    access to be used and determines whether the file can be shared.
    The Open service also performs an implicit Display service. The
    maximum number of files that can be open within an image at one
    time is 16383.

    Format

      SYS$OPEN  fab [,[err] [,suc]]

  Additional Information (explode) :

• Returns
• Arguments
• Condition Values Returned