Node:C strings, Previous:Short strings, Up:Strings in GPC

#### What about C strings?

A C string (`char *`) is an array of char, terminated with a `#0` char.

C library functions require C, not Pascal style string arguments. However, Pascal style strings are automatically converted to C style strings when passed to a routine that expects C style strings. This works only if the routine reads from the string, not if it modifies it.

E.g., this is how you could access the `system()` call in your C library (which is not necessary anymore, since `Execute` is already built-in):

    program SysCall;

    function System (CmdLine: CString): Integer; external name 'system';

    var
      Result: Integer;

    begin
      Result := System ('ls -l');
      WriteLn ('system() call returned: ', Result)
    end.

You could use the type `PChar` instead of `CString`. Both `CString` and `PChar` are predefined as `^Char` - though we recommend `CString` because it makes it clearer that we're talking about some kind of string rather than a single character.

A lot of library routines in Pascal for many applications exist in the GPC unit and some other units. Where available, they should be preferred (e.g. `Execute` rather than `system()`, and then you won't have to worry about `CString`s.)

Do not pass a C style string as a `const` or `var` argument if the C prototype says `const char *` or you will probably get a segfault.