Slide 5.14: TEXTEQU directive Slide 6.2: A sample program: finding Fibonacci numbers Home

Data Transfer Instructions

Instruction	Description	Example
MOV	Copies data from a source operand to a destination operand.	mov eax, ebx
MOVZX	Copies the contents of a source operand into a destination operand and zero-extends the value to either 16 or 32 bits.	movzx eax, bx
MOVSX	Copies the contents of a source operand into a destination operand and sign-extends the value to either 16 or 32 bits.	movsx eax, bl
LAHF	Copies the low byte of the EFLAGS register into AH.	lahf
SAHF	Copies AH into the low byte of the EFLAGS register.	sahf
XCHG	Exchanges the contents of two operands	xchg ah, al

Basic Program Execution Registers

32-bit 16-bit 16-bit   SI ESI   32-bit 16-bit 16-bit   DI EDI   32-bit 16-bit 16-bit   BP EBP   32-bit 16-bit 16-bit   SP ESP

• ESP (Extended Stack Pointer) addresses data on the stack.
• ESI (Extended Source Index) is used by high-speed memory transfer.
• EDI (Extended Destination Index) is used by high-speed memory transfer.
• EBP (Extended Frame Pointer) is used by high-level languages to reference function parameters and local variables on the stack.
• Segment registers are used as base locations for preassigned memory called segments.
• EIP (Extended Instruction Pointer) contains the address of the next instruction to be executed.