>Can you quote the relevant portion of the standard that relates to that Prelude?
184.108.40.206 The fseek function
int fseek(FILE *stream, long int offset, int whence);
The fseek function sets the file position indicator for the stream pointed to by stream.
If a read or write error occurs, the error indicator for the stream is set and fseek fails.
For a binary stream, the new position, measured in characters from the beginning of the
file, is obtained by adding offset to the position specified by whence. The specified
position is the beginning of the file if whence is SEEK_SET, the current value of the file
position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
meaningfully support fseek calls with a whence value of SEEK_END.