The Selector Registers

Each selector register appears to be 16 bits long. The six application selector registers and a brief description of the use for each follow:

SS: Stack Selector, specifies the descriptor used for stack references.

CS: Code Selector, specifies the descriptor used for instruction references.

DS: Data Selector, specifies the descriptor used for most data references.

ES: Extra Selector, specifies another descriptor used for data references.

FS: This is a selector which can be used for data references if explicitly specified.

GS: This is a selector which can be used for data references if explicitly specified.

LDTR: The LDT register selects the LDT descriptor from the GDT.

TR: The Task Register selects the descriptor used for the TSS.