Previous: iopnam Up: ../plot79_i.html Next: iopopn
INTEGER FUNCTION IOPOPF (FNAME,LENFNM,MODEOP)
C$ (Open File by Name or Number)
C$ This routine is called to open a file by name or number.
C$ If the token following the command keyword is numeric, it
C$ is taken to be an integer to be used as a FORTRAN unit
C$ number for further input, which is a portable usage
C$ (subject to CDC's requirement of declaration of all files
C$ in the PROGRAM statement of the main program). If it is
C$ alphanumeric, then it is assumed to be a system-dependent
C$ file name which must be associated with a FORTRAN unit
C$ number created for the purpose.
C$
C$ The function value returned for a successful open is a
C$ valid FORTRAN unit number greater than 0, and that number
C$ has been pushed onto the top of the file stack in COMMON.
C$ If the open fails, then -1 is returned.
C$
C$ The code section which actually calls for an OPEN command
C$ to be executed is thus system-dependent, and may not be
C$ supportable in all environments. It is localized entirely
C$ in routine IOPOPN. It is useful to provide that support
C$ when the host permits it (as all FORTRAN 77 hosts must).
C$ The search for a usable file number should be completely
C$ portable, subject perhaps to the largest and smallest
C$ FORTRAN unit numbers defined as MINUNO and MAXUNO below.
C$ If runtime file opening by name is not possible, IOPOPN can
C$ simply be a dummy routine which returns the value -1.
C$
C$ (28-JUN-82)