<page_title> X86-64 </page_title> <section_title> Operating modes </section_title> <table> <cell> 64-bit mode <col_header> Operating sub-mode </col_header> </cell> <cell> 64-bit <col_header> Operating system required </col_header> </cell> <cell> 64-bit code <col_header> Type of code being run </col_header> </cell> <cell> Compatibility mode <col_header> Operating mode </col_header> </cell> <cell> 32-bit code <col_header> Operating sub-mode </col_header> </cell> <cell> 16-bit code <col_header> Operating mode </col_header> </cell> </table>
Under a 64-bit operating system, 64-bit programs run under 64-bit mode, and 32-bit and 16-bit run under compatibility mode.