Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!munnari.oz.au!uhccux!tholen
From: tholen@uhccux.uhcc.Hawaii.Edu (David Tholen)
Newsgroups: comp.lang.fortran
Subject: Re: File handling in Fortran 77
Message-ID: <9665@uhccux.uhcc.Hawaii.Edu>
Date: 3 Oct 90 08:40:31 GMT
References: <28454@pasteur.Berkeley.EDU>
Organization: University of Hawaii
Lines: 17

In article <28454@pasteur.Berkeley.EDU>, ndeng@euler.Berkeley.EDU writes:
                                      
> Correct me if I am wrong. But how could one CONNECT to a file before OPEN it?
  
Simple.  OPEN it twice without CLOSEing it in between.  The file will be
connected before the second OPEN.  Many systems preconnect some or all units.
For example, many compilers do not require you to OPEN the keyboard to
accept input or OPEN the screen (or printer) to print output.  UNIX systems
preconnect logical units 0, 5, and 6, to standard error, standard input, and
standard output, respectively.  Some UNIX FORTRANS preconnect all other units
to files with names 'fort.N', where N corresponds to the logical unit number.
Thus if you WRITE to a logical unit number that hasn't been explicitly
OPENed, the output will go to the file 'fort.N'.  Any file that has been
preconnected will be connected at the time of an explicit OPEN statement.

So why would somebody want to OPEN a file that is already OPENed?  Simply to
change the connection properties, such as BLANK='NULL' to BLANK='ZERO'.