open or fopen?

["Eric Fisher" <joefoxreal@xxxxxxxxx>]

hi,
There is a question about file operation functions used in gcc source
code. I can't figure out why sometimes we use open function such as
load_specs in gcc.c,
static char *
load_specs (const char *filename)
{
 int desc;
 ...
 /* Open and stat the file.  */
 desc = open (filename, O_RDONLY, 0);
 ...
}
why not fopen?

Thanks