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2. Segment Registers Revisited

  • Segment Registers in Protected Mode separate different blocks of code and data to protect them from undesirable interactions.

  • CS (Code Segment) contains processor instructions and their immediate operands.

  • DS (Data Segment) normally contains data allocated by the program.

  • SS (Stack Segment) contains the program stack for use by PUSH, POP, CALL, and RET.

  • ES (Extra Segment) references secondary data segment. Used by string instructions.

  • FS, GS provide extra segments on 80386/486/Pentium.

  • The six segments of the memory system:

      The six segments of the memory system

    Segmented architecture is an important part of Linux and Windows memory-protection schemes.

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