The MOV Instruction

The MOV Instruction

mov is the most fundamental x86_64 instruction. It copies data from a source to a destination.

Forms of MOV

mov reg, imm       ; Load immediate value into register
mov reg, reg       ; Copy register to register
mov reg, [mem]     ; Load from memory into register
mov [mem], reg     ; Store register into memory
mov [mem], imm     ; Store immediate into memory

Memory Addressing

x86_64 has powerful addressing modes:

mov rax, [rbx]         ; Simple: address in rbx
mov rax, [rbx + 8]     ; Base + displacement
mov rax, [rbx + rcx]   ; Base + index
mov rax, [rbx + rcx*4] ; Base + scaled index

LEA vs MOV

lea (Load Effective Address) computes an address but does not access memory:

lea rax, [msg]     ; rax = address of msg (no memory access)
mov rax, [msg]     ; rax = value AT address of msg (memory access)

The EQU Directive

You can define constants with equ:

msg db "Hello", 10
msglen equ 6       ; constant: length of msg

Your Task

Write a program that defines two strings in the data section and prints them both. First print "x86_64 " (7 chars), then print "Assembly\n" (9 chars).