Editing Magic number (programming) (section)

== GUIDs {{anchor|Magic GUIDs}} ==
It is possible to create or alter [[globally unique identifier]]s (GUIDs) so that they are memorable, but this is highly discouraged as it compromises their strength as near-unique identifiers.<ref>{{cite web |url=http://www.developerfusion.co.uk/show/1713/4/ |title=Message Management: Guaranteeing uniqueness |first=Joseph M. |last=Newcomer |date=13 October 2001 |work=Developer Fusion |access-date=2007-11-16 |archive-url=https://web.archive.org/web/20050421023819/https://www.developerfusion.com/show/1713/4/ |archive-date=21 April 2005 |url-status=dead }}</ref><ref>{{cite web |url=https://learn.microsoft.com/en-us/archive/blogs/larryosterman/uuids-are-only-unique-if-you-generate-them |title=UUIDs are only unique if you generate them... |first=Larry |last=Osterman |date=21 July 2005 |work=Larry Osterman's WebLog - Confessions of an Old Fogey |publisher=MSDN |access-date=2007-11-16 |archive-url=https://web.archive.org/web/20230328134453/https://learn.microsoft.com/en-us/archive/blogs/larryosterman/uuids-are-only-unique-if-you-generate-them |archive-date=28 March 2023 |url-status=live }}</ref> The specifications for generating GUIDs and UUIDs are quite complex, which is what leads to them being virtually unique, if properly implemented.<ref>{{cite web | url=https://datatracker.ietf.org/doc/html/rfc9562 | title=RFC 9562 - Universally Unique IDentifiers (UUIDs) | date=May 2024 | website=ietf.org | access-date=9 August 2024 }}</ref>

Microsoft Windows product ID numbers for [[Microsoft Office]] products sometimes end with <code>0000-0000-0000000FF1CE</code> ("OFFICE"),  such as {<code>90160000-008C-0000-0000-0000000FF1CE</code>}, the product ID for the "Office 16 Click-to-Run Extensibility Component".

Java uses several GUIDs starting with <code>CAFEEFAC</code>.<ref>{{cite web |url=https://www.oracle.com/java/technologies/javase/family-clsid.html |title=Deploying Java Applets With Family JRE Versions in Java Plug-in for Internet Explorer |publisher=[[Oracle Corporation|Oracle]] |access-date=28 March 2023 |archive-url=https://web.archive.org/web/20221130180350/https://www.oracle.com/java/technologies/javase/family-clsid.html |archive-date=30 November 2022 |url-status=live }}</ref>

In the [[GUID Partition Table]] of the GPT partitioning scheme, [[BIOS Boot partition]]s use the special GUID {<code>21686148-6449-6E6F-744E-656564454649</code>}<ref>{{cite web |url=https://www.gnu.org/software/grub/manual/html_node/BIOS-installation.html |title=GNU GRUB Installation, Section 3.4: BIOS installation |access-date=2014-06-26 |website=Gnu.org |archive-url=https://web.archive.org/web/20230315232257/https://www.gnu.org/software/grub/manual/grub/html_node/BIOS-installation.html |archive-date=15 March 2023 |url-status=live }}</ref> which does not follow the GUID definition; instead, it is formed by using the [[ASCII]] codes for the string "<code>Hah!IdontNeedEFI</code>" partially in [[little endian]] order.<ref>{{cite web |url=https://www.howtogeek.com/201059/magic-numbers-the-secret-codes-that-programmers-hide-in-your-pc/ |title=Magic Numbers: The Secret Codes that Programmers Hide in Your PC |first=Lowell |last=Heddings |date=3 November 2014 |work=How-To Geek |access-date=3 October 2017 |archive-url=https://web.archive.org/web/20230326024750/https://www.howtogeek.com/201059/magic-numbers-the-secret-codes-that-programmers-hide-in-your-pc/ |archive-date=26 March 2023 |url-status=live }}</ref>