Segmentation and the Global Descriptor Table (GDT)
Learn how x86 segmentation works alongside paging: segment selectors, descriptors, the GDT, and how flat memory models set the stage for protected mode.
What Is Segmentation?
Segmentation divides memory into variable-sized regions called segments, each with a base address, limit, and access rights. It predates paging and is the first translation step in x86 address generation.
Real Mode Segments
In 16-bit real mode, a physical address is computed as segment * 16 + offset. This gave access to 1 MB using 16-bit registers but offered no protection at all.
All lessons in this course
- Paging and Memory Management Unit (MMU)
- Protection Rings and Privileges
- Hypervisors and Virtualization Basics
- Segmentation and the Global Descriptor Table (GDT)