The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
All other sections in this Literature Study Guide are owned and copyrighted by BookRags, Inc.
Privileged instruction is an instruction (usually in machine code) that can be executed only by the operating system in a specific mode. (An instruction is a statement that is acted upon by any computer language.) Examples of where privileged instructions are used include operations involving input/output and memory management (the coordinated effort to provide sufficient memory to all processes of a computer system). The existence of privileged instructions is to specifically allow the operating system to perform certain operations that applications should not be allowed to perform. To allow for privileged instructions a "mode bit" is added into the computer's software to indicate one of two dual modes: monitor mode or user mode. The privileged instruction can only be executed when the microprocessor is running in monitor (or supervisor) mode, a mode that enables execution of all instructions. Thus, the operating system contains routines that execute these particular (privileged) instructions. The monitor mode is the normal operating state of computers. If an attempt is made to execute a privileged instruction in the user state, then the microprocessor does not execute the instruction. The user mode is the least privileged of the states, being the state from which all application programs run.