In the multitasking environment, enough protection is necessary to ensure that multitasking is reliable. In end-user systems, the operating system should be protected against damage from user programs or should recover automatically. The i386/i486 processor uses privilege levels to implement such protection. Each task has four privilege levels, numbered from 0 to 3. Lesser numbers mean higher privilege levels. This chapter discusses the definition of privilege level and its effect during control transfers between different processes and different privilege levels.
KeywordsTask Switch Segment Register Target Segment Code Segment Control Transfer
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