Assembly Language - Programmer Sheet

Copying Data

Instruction	Effect	Examples
mov src,dest	Copy src to dest	mov $10,%eax movw %eax,(2000)

Arithmetic

Instruction	Effect	Examples
add src,dest	dest = dest + src	add $10, %esi
sub src,dest	dest = dest – src	sub %eax,%ebx
mul reg	edx:eax = eax * reg	mul %esi
div reg	edx = edx:eax mod reg eax = edx:eax ÷ reg	div %edi
inc dest	Increment destination	inc %eax
dec dest	Decrement destination	dec (0x1000)

Function Calls

Instruction	Effect	Examples
call label	Push eip, transfer control	call format_disk
ret	Pop eip and return	ret
push item	Push item (constant or register) to stack	pushl $32 push %eax
pop [reg]	Pop item from stack; optionally store to register	pop %eax popl

Bitwise Operations

Instruction	Effect	Examples
and src,dest	dest = src & dest	and %ebx, %eax
or src,dest	dest = src \| dest	orl (0x2000),%eax
xor src,dest	dest = src ^ dest	xor $0xffffffff,%ebx
shl count,dest	dest = dest << count	shl $2,%eax
shr count,dest	dest = dest >> count	shr $4,(%eax)

Conditionals and Jumps

Instruction	Effect	Examples
cmp arg1,arg2	Compare arg1 to arg2; must immediately precede any of the conditional jump instructions	cmp $0,%eax
je label	Jump to label if arg1 == arg2	je endloop
jne label	Jump to label if arg1 != arg2	jne loopstart
jg label	Jump to label if arg2 > arg1	jg exit
jge label	Jump to label if arg2 > arg1	jge format_disk
jl label	Jump to label if arg2 < arg1	jl error
jle label	Jump to label if arg2 < arg1	jle finish
test reg,imm	Bitwise compare of register and constant; must immediately precede the jz or jnz instructions	test $0xffff,%eax
jz label	Jump to label if bits were not set (“zero”)	jz looparound
jnz label	Jump to label if bits were set (“not zero”)	jnz error
jmp label	Unconditional relative jump	jmp exit
jmp *reg	Unconditional absolute jump; arg is a register	jmp *%eax
ljmp segment,offs	Unconditional absolute far jump	ljmp $0x10,$0

Miscellaneous

Instruction	Effect	Examples
nop	No-op (opcode 0x90)	nop
hlt	Halt the CPU	hlt

Suffixes: b=byte (8 bits); w=word (16 bits); l=long (32 bits). Optional if instruction is unambiguous.
Arguments to instructions: Note that it is not possible for both src and dest to be memory addresses.
Constant (decimal or hex):$10 or $0xff Fixed address:(2000) or (0x1000+53)
Register:%eax %bl Dynamic address:(%eax) or 16(%esp)
32-bit registers: %eax, %ebx, %ecx, %edx, %esi, %edi, %esp, %ebp
16-bit registers: %ax, %bx, %cx, %dx, %si, %di, %sp, %bp
8-bit registers: %al, %ah, %bl, %bh, %cl, %ch, %dl, %dh