Editing Protected mode (section)

{{short description|Operational mode of x86-compatible CPUs}}
{{about|the x86 processor mode|Internet Explorer Protected Mode|Mandatory Integrity Control}}
{{distinguish|text = [[Safe mode]], a diagnostic mode in operating systems}}
{{x86 Processor Modes}}

In computing, '''protected mode''', also called '''protected virtual address mode''',<ref name="'Protected virtual address mode' usage">{{ cite web | url = http://www.patentstorm.us/patents/5483646-claims.html | title = Memory access control method and system for realizing the same | work = US Patent 5483646 | access-date = 2007-07-14 | date = May 23, 1995 | format = Patent | quote = The memory access control system according to claim 4, wherein said first address mode is a real address mode, and said second address mode is a protected virtual address mode. | url-status = dead | archive-url = https://web.archive.org/web/20070926220520/http://www.patentstorm.us/patents/5483646-claims.html | archive-date = September 26, 2007 }}</ref> is an operational mode of [[x86]]-compatible [[central processing unit]]s (CPUs). It allows [[system software]] to use features such as [[Memory_segmentation|segmentation]], [[virtual memory]], [[paging]] and safe [[computer multitasking|multi-tasking]] designed to increase an operating system's control over [[application software]].<ref name="i386 additions">{{ cite book | title = Intel 64 and IA-32 Architectures Software Developer's Manual Volume 1: Basic Architecture | publisher = [[Intel]] | at = Section 2.1.3 The Intel 386 Processor (1985) |date=May 2019 | url = https://software.intel.com/en-us/download/intel-64-and-ia-32-architectures-software-developers-manual-volume-1-basic-architecture }}</ref><ref name="Purpose of protected mode">{{ cite web | url = http://www.delorie.com/djgpp/doc/ug/basics/protected.html | title = Guide: What does protected mode mean? | access-date = 2007-07-14 | author = root | date = July 14, 2007 | format = Guide | publisher = [[Delorie Software]] | quote = The purpose of protected mode is not to protect your program. The purpose is to protect everyone else (including the operating system) from your program. }}</ref>

When a processor that supports x86 protected mode is powered on, it begins executing instructions in [[real mode]], in order to maintain [[backward compatibility]] with earlier x86 processors.<ref name="Real mode on powered on">{{ cite book | title = Intel 64 and IA-32 Architectures Software Developer's Manual Volume 1: Basic Architecture | publisher = [[Intel]] | at = Section 3.1 Modes of Operation |date=May 2019 | url = https://software.intel.com/en-us/download/intel-64-and-ia-32-architectures-software-developers-manual-volume-1-basic-architecture }}</ref> Protected mode may only be entered after the system software sets up one descriptor table and enables the Protection Enable (PE) [[bit]] in the [[control register]] 0 (CR0).<ref name="Entering protected mode">{{Cite FTP | url = ftp://ftp.utcluj.ro/pub/users/nedevschi/PMP/protected86/collinsprot.PDF | title = Protected Mode Basics | access-date = 2009-07-31 | last = Collins | first = Robert | date = 2007 | url-status = dead | server = ftp.utcluj.ro }}</ref>

Protected mode was first added to the [[x86]] architecture in 1982,<ref name="i286 release date">{{ cite book | title = Intel 64 and IA-32 Architectures Software Developer's Manual Volume 1: Basic Architecture | publisher = [[Intel]] | at = Section 2.1.2 The Intel 286 Processor (1982) |date=May 2019 | url = https://software.intel.com/en-us/download/intel-64-and-ia-32-architectures-software-developers-manual-volume-1-basic-architecture }}</ref> with the release of [[Intel]]'s [[80286]] (286) processor, and later extended with the release of the [[80386]] (386) in 1985.<ref name="i386 release date">{{ cite web | url = http://www.intel.com/intel/finance/gcr03/39-years_of_innovation.htm | title = Intel Global Citizenship Report 2003 | access-date = 2007-07-14 | format = Timeline | quote = 1985 Intel launches Intel386 processor | archive-url = https://web.archive.org/web/20080322075839/http://www.intel.com/intel/finance/gcr03/39-years_of_innovation.htm | archive-date = 2008-03-22 }}</ref> Due to the enhancements added by protected mode, it has become widely adopted and has become the foundation for all subsequent enhancements to the x86 (IA-32) architecture,<ref name="Foundation">{{ cite book | title = Intel 64 and IA-32 Architectures Software Developer's Manual Volume 1: Basic Architecture | publisher = [[Intel]] | at = Section 2.1 Brief History of Intel 64 and IA-32 Architecture |date=May 2019 | url = https://software.intel.com/en-us/download/intel-64-and-ia-32-architectures-software-developers-manual-volume-1-basic-architecture }}</ref> although many of those enhancements, such as added instructions and new registers, also brought benefits to the real mode.