HELP !_(re)

Thu, 2 Nov 1995 09:14:13 -0500 (EST)

On Thu, 2 Nov 1995, Mauro Ottaviani wrote:
> Hello,
> I have a problem using files with gpc:
> In Turbo Pascal I usually use the following:
> var
>    f:text;
> begin
>    assign(f,'filename');
>    reset(f);
>    ...
>    close(f);
> But this doesn't work with gpc !!
> I tryed:
>    reset(f,'filename');
> This time it also compiled OK, but gives a runtime error !!
> Please HELP me !

	
	In ISO Pascal, you have to specify any external files accessed by 
your program in the Program header.  For example:

	Program Demo1 (InFile, OutFile);

  	Var
         InFile, OutFile : Text;

        Begin
         Reset (InFile);
         Rewrite (OutFile);
        End {Demo1}.

'Tho ISO Pascal has no provisions for specifying a filename for the 
external files, most Pascal implementations allow you to do so via the 
Reset/Rewrite commands.  GPC is one of these Pascal implementations.  So, 
modifying the above program to open the files "INDATA" for input and 
"OUTDATA" for output:

	Program Demo2 (InFile, OutFile);

  	Var
         InFile, OutFile : Text;

        Begin
         Reset (InFile, './INDATA');
         Rewrite (OutFile, './OUTDATA');
        End {Demo2}.

In ISO Pascal, files are automatically closed when the program 
terminates, therefore there is no "Close" command.  Some Pascal 
implementations, like Borland, do have a "Close" command.  I don't know 
if GPC has one or not.

Also, the files "Input" and "Output" are special files used for standard 
input and standard output respectivly.  So to use Read/Readln and 
Write/Writeln to get input from the keyboard and to display something on 
the screen, you have to put a "Input, Output" in your program header.

A little different from Borland, I know.  But actually, if you think 
about it, it's a little better to specify what external files are used in 
the Program header.  That way you know exactly what files are gonna be 
opened by just looking at the Program header.  I didn't like it at first, 
but now I think it's not a bad idea.


Arcadio

Arcadio Alivio Sincero (lotu@wam.umd.edu)