Register Summary The register prefix refers to the full 32-bit registe

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Register Summary
The E register prefix refers to the full 32-bit register (386+).
Accumulator [E]AX (AH/AL) Multiply, divide, I/O, fast
arithmetic
Base [E]BX (BH/BL) Pointer to base address (data
segment)
Count [E]CX (CH/CL) Count for loops, repeats, and shifts
Data [E]DX (DH/DL) Multiply, divide, and I/O
Source Index [E]SI Source string and index pointer
Destination Index [E]DI Destination string and index pointer
Base Pointer [E]BP Pointer to stack base address
Stack Pointer [E]SP Pointer to top of stack
Flags [E]<Flags> Processor flags
Instruction Pointer [E]IP Memory location of current
instruction
Code Segment CS Segment containing program code
Data Segment DS Segment containing program data
Stack Segment SS Segment for stack operations
Extra Segment ES Extra program data segment
" FS Extra program data segment (386+)
" GS Extra program data segment (386+)
Control Registers CR(0-3) Paging, caching, and
protection (386+)
Debug Registers DR(0-7) Data and instruction
breakpoints (386+)
Test Registers TR(3-7) Testing the TLB and cache (386+)
Global Descriptor GDTR Address and limit of GDT (286+)
Local Descriptor LDTR Address, limit, and selector of
LDT (286+)
Interrupt Descriptor IDTR Address and limit of IDT (286+)
Task Register TR Address, limit, selector, and
attributes of current task