CPU Registers

This is a quick lookup page for assembly language programming.

Registers

Register	Description	Bitwidth (bit)
AX	Accumulator	16
CX	Counter	16
DX	For Data address	16
BX	For Base address	16
SP	Stack pointer	16
BP	Base pointer	16
SI	Source index	16
DI	Destination index	16
AL	Low 8 bits of AX	8
AH	High 8 bits of AX	8
CL	Low 8 bits of CX	8
CH	High 8 bits of CX	8
DL	Low 8 bits of DX	8
DH	High 8 bits of DX	8
BL	Low 8 bits of BX	8
BH	High 8 bits of BX	8
EAX	Extended Accumulator	32
ECX	Extended Counter	32
EDX	Extended Data address	32
EBX	Extended Base address	32
ESP	Extended Stack pointer	32
EBP	Extended Base pointer	32
ESI	Extended Source index	32
EDI	Extended Destination index	32

Flags

ZF	Zero flag	1
OF	Overflow flag	1
CF	Carry flag	1
SF	Sign flag	1

Segment Registers

ES	Extra segment	16
CS	Code segment	16
SS	Stack segment	16
DS	Data segment	16
FS	Segment part 2	16
GS	Segment part 3	16