...
const
FILE_NAME = 'C:\PRUEBA.TXT';
var
Hnd: Integer;
stToRead: shortString;
NR: LongWord;
begin
Hnd:= CreateFile(FILE_NAME, GENERIC_READ + GENERIC_WRITE,
FILE_SHARE_READ + FILE_SHARE_WRITE, 0,
OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
Readfile(Hnd, stToRead, SizeOf(stToRead), NR, nil);
CloseHandle(Hnd);
ShowMessage(stToRead);
end;