Editing ISO 9660 (section)

=== El Torito ===
''El Torito'' is an extension designed to allow [[booting]] a computer from a CD-ROM. It was announced in November 1994<ref>{{cite press release | title = Phoenix announces bootable CD-ROM specification; Specification developed jointly by Phoenix and IBM | publisher = Phoenix Technologies Ltd. | date = 1994-11-11 | url = http://www.thefreelibrary.com/Phoenix+announces+bootable+CD-ROM+specification%3b+Specification...-a015922225 | access-date = 2008-01-31 | archive-date = 10 August 2017 | archive-url = https://web.archive.org/web/20170810051304/https://www.thefreelibrary.com/Phoenix+announces+bootable+CD-ROM+specification%3b+Specification...-a015922225 | url-status = dead }}</ref> and first issued in January 1995 as a joint proposal by [[IBM]] and BIOS manufacturer [[Phoenix Technologies]]. According to legend, the El Torito CD/DVD extension to ISO 9660 got its name because its design originated in an [[El Torito]] restaurant in [[Irvine, California]] ({{CoordDec|33.684722|-117.852547}}).<ref name="Parker">{{ cite news | last = Parker | first = Dana J. | title = Fresh Tortillas and CD-ROM Standards: The El Torito Bootable CD-ROM Specification | periodical = CD-ROM Professional | volume = 8 | issue = 7 | url = http://www.cdpage.com/Compact_Disc_Variations/danaboot.html | archive-url = https://web.archive.org/web/19991008045553/http://www.cdpage.com/Compact_Disc_Variations/danaboot.html | access-date = 2008-01-31 | archive-date = 1999-10-08 }}</ref> The initial two authors were Curtis Stevens, of Phoenix Technologies, and Stan Merkin, of IBM.<ref name="Parker" />

A 32-bit PC BIOS will search for boot code on an ISO 9660 CD-ROM. The standard allows for booting in two different modes. Either in hard disk emulation when the boot information can be accessed directly from the CD media, or in floppy emulation mode where the boot information is stored in an [[disk image|image file]] of a [[floppy disk]], which is loaded from the CD and then behaves as a virtual floppy disk. This is useful for computers that were designed to boot only from a floppy drive. For modern computers the "no emulation" mode is generally the more reliable method. The BIOS will assign a BIOS drive number to the CD drive. The drive number (for [[INT 13H]]) assigned is any of 80<sub>hex</sub> ([[hard disk]] emulation), 00<sub>hex</sub> ([[floppy disk]] emulation) or an arbitrary number if the BIOS should not provide emulation. Emulation is useful for booting older [[operating system]]s from a CD, by making it appear to them as if they were booted from a hard or floppy disk.<ref name=osdev/>

[[UEFI]] systems also accept El Torito records, as platform 0xEF. The record is expected to be a disk image containing a FAT filesystem, the filesystem being an [[EFI System Partition]] containing the usual {{code|\EFI}} directory. The image should be marked for "no emulation", though it does not actually work like the BIOS "no emulation" mode, in which the BIOS would load the image in memory and execute the code from there.<ref>{{cite web |title=13. Protocols – Media Access — UEFI Specification 2.10 documentation |url=https://uefi.org/specs/UEFI/2.10/13_Protocols_Media_Access.html#partition-discovery |website=uefi.org}}</ref>

El Torito can also be used to produce CDs which can boot up [[Linux]] operating systems, by including the [[GRUB]] bootloader on the CD and following the [[Multiboot Specification]].<ref name=osdev>{{ cite web | url = http://wiki.osdev.org/El-Torito | title = El-Torito | work = OSDev | access-date = 2015-01-03 }}</ref> While the El Torito spec alludes to a "Mac" platform ID, PowerPC-based Apple Macintosh computers don't use it.<ref>{{cite web | url = http://www.macdisk.com/hybbooten.php | title = Bootable hybrid (ISO/HFS) CD-ROMs | access-date = 2014-01-03 }}</ref>