Protected Mode

In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units (CPU). It allows system software to use features such as virtual memory, paging and safe multi-tasking designed to increase an operating system's control over application software.

When a processor that supports x86 protected mode is powered on, it begins executing instructions in real mode, in order to maintain backwards compatibility with earlier x86 processors. Protected mode may only be entered after the system software sets up several descriptor tables and enables the Protection Enable (PE) bit in the control register 0 (CR0).

Protected mode was first added to the x86 architecture in 1982, with the release of Intel's 80286 (286) processor, and later extended with the release of the 80386 (386) in 1985. 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 architecture.

Read more about Protected Mode:  History, 386 Additions To Protected Mode, Entering and Exiting Protected Mode, Features, Operating Systems

Other articles related to "protected mode, protected, modes, mode":

Protected Mode - Operating Systems
... Operating systems like OS/2 1.x try to switch the processor between protected and real modes ... This is both slow and unsafe, because a real mode program can easily crash a computer ... rules allowing a Family API or bound program to run in either real or protected mode ...
Windows 2.1x - Editions - Windows/386
... It introduced a protected mode kernel, above which the GUI and applications run as a virtual 8086 mode task ... allowed several MS-DOS programs to run in parallel in "virtual 8086" CPU mode, rather than always suspending background applications ... have their own extended memory management and run in protected mode as well ...
Windows 3.0 - Features
... Text-mode programs written for MS-DOS could be run within a window (a feature previously available in a more limited form with Windows/386 2.1), making the system usable as a crude multitasking base for legacy ... support a full 16 colors in EGA and VGA mode while Windows 2.x only had colored menus and window boxes with in-application graphics being monochrome. 256 color VGA mode was supported for the first time ...
Interrupt Descriptor Table - Protected Mode
... In protected mode, the IDT is an array of 8-byte descriptors stored consecutively in memory and indexed by an interrupt vector ... The protected mode IDT may reside anywhere in physical memory ...
Multiuser DOS - Concurrent DOS - Concurrent DOS 286 and FlexOS
... The operating system would function strictly in 80286 native mode, allowing protected mode multi-user, multitasking operation while running 8086 emulation ... would not allow Concurrent DOS 286 to run 8086 software in protected mode ... approach Digital Research wished to take in emulating 8086 software in protected mode differed from the original specifications nevertheless they incorporated ...

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