.::ALU/CPU Registers::.

• The Pentium processor has 16 registers for use in general programming
  • Eight 32-bit general purpose data registers
  • Six 16-bit segment registers
  • Two 32-bit status and control registers

• The general purpose data registers are used for holding:
  • Operands for logical and arithmetic operations
  • Operands for address calculations
  • Memory pointers

• General purpose registers:
  • EAX - Accumulator for operands and results
  • EBX - Pointer to data in the DS segment
  • ECX - Counter for loop operations
  • EDX - Input/output pointer
  • ESI - Pointer to data in the DS segment
  • EDI - Pinter to data in the ES segment
  • ESP - Stack pointer (SS segment)
  • EBP - Pointer to data on the stack (SS segment)

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32-bit	16-bit	high bytes	low bytes
EAX	AX	AH	AL
EBX	BX	BH	BL
ECX	CX	CH	CL
EDX	DX	DH	DL
ESI	SI
EDI	DI
ESP	SP
EBP	BP

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• Segment registers identify a particular segment in main memory. There is the code segment, the stack segment, and four data segments:
  • CS - code segment
  • SS - stack segment
  • DS - data segment
  • ES - data segment
  • FS - data segment
  • GS - data segment

• Status and control registers:
  • EFLAGS - Contains a group of status flags, a control flag, and a group of system flags.
  • EIP - The instuction pointer register contains the offset in the current code segment for the next instruction