Intel 64 and IA-32 Architectures Software Developers Manual Volume 1, Basic Architecture

Vol. 1 3-15
BASIC EXECUTION ENVIRONMENT
The special uses of general-purpose registers by instructions are described in
Chapter 5, “Instruction Set Summary,” in this volume. See also: Chapter 3 and
Chapter 4 of Intel® 64 and IA-32 Architectures Software Developer’s Manual,
Volumes 2A & 2B. The following is a summary of special uses:
• EAX — Accumulator for operands and results data
• EBX — Pointer to data in the DS segment
• ECX — Counter for string and loop operations
• EDX — I/O pointer
• ESI — Pointer to data in the segment pointed to by the DS register; source
pointer for string operations
• EDI — Pointer to data (or destination) in the segment pointed to by the ES
register; destination pointer for string operations
Figure 3-4. General System and Application Programming Registers
031
EAX
EBX
ECX
EDX
ESI
EDI
EBP
ESP
Segment Registers
CS
DS
SS
ES
FS
GS
0
15
0
31
EFLAGS
EIP
31
0
General-Purpose Registers
Program Status and Control Register
Instruction Pointer