Lab 1 - Intro to ASM&Signed Integers

$$\begin{array}{rl}-3=10000011_{(2)}& ⟹-3+3\ne 0\stackrel{flipbits}{\to }\\ 11111100_{(2)}& ⟹-3+3\ne 0\stackrel{add1}{\to }\\ 11111101_{(2)}& ⟹-3+3=0\end{array}$$

Common registers: EAX,EBX,ECX,EDX

mov al, 5
mov al, 17
mov ah, 5

Types of registers

• ah or al are small, 1 byte registers (A high or A low)
• ax is a 2 byte register, equal in size to a word
• eax is a 4 byte, double word register

Types of "variables"

• db=1 byte
• dw=2 bytes (word)
• dd = 4 bytes (double word)

Important

Computer memory is little-endian, registers are big-endian, i.e. memory is read back to front. This is done for optimization reasons

Bases in assembly

• numbers are implicitly decimal (D,d)
• base 2, binary (B,b)
• base 8, octal (O,o)
• base 16, hexa, (H,h)