While I'm not familiar with a C_System function, if is in written in C, you
most likely should be passing a C string:

    function C_System(value : Interfaces.C.Char_Array) return integer;
    pragma Import(
          C, C_System, "system");
    result : integer;
 begin
    result := C_System( Interfaces.C.To_C( "pwd " ) );
    result := C_System( Interfaces.C.To_C( "acdsee
D:\work\pictures\BP47.jpg" ) );
 end Command;

This turns the Ada string, which includes information about the extent of
the string, into a null terminated string.

Other answers to questions:
  You may import functions or procedures.
  Passing file handles from Ada to C may be tricky.  If you use the
File_Type defined in Ada's standard libraries, the definition is
implementation dependent.  You can certainly interface to C functions for
doing all I/O in Ada, but I don't know if you can mix Ada and C's native
file handling.

I hope this helps,

SteveD

"Torbj�rn Karfunkel" <toka@prover.com> wrote in message
news:mailman.989509930.7705.comp.lang.ada@ada.eu.org...
> Using the pragma Import method of calling non-Ada entities, am I only
> allowed to define functions? How about procedures? What I want to do is
> to create a text file, give this text file as a parameter to a C
> program, and then wait until the C program finishes. By then it will
> have produced another text file that I want to use.
> Can I use a dummy result variable like the 'result' in the following
> (from another mail):
>
> procedure Command is
>
>    function C_System(value : String) return integer;
>    pragma Import(
>          C, C_System, "system");
>
>    result : integer;
> begin
>    result := C_System("pwd ");
>    result := C_System(value => "acdsee D:\work\pictures\BP47.jpg ");
> end Command;
>
> /Torbj�rn Karfunkel
>
>
>