Common Instructions

Question 1

What does “ADD op1, op2” mean?

Answer 1

Add operand 1 and operand 2 together and store in operand 1.

Question 2

What does “SUB op1, op2” mean?

Answer 2

Subtract operand 2 from operand 1 and store in operand 1.

Question 3

What values can be operands be in the ADD/SUB instructions?

Answer 3

Registers, memory locations (limited to one) or constant values.

Question 4

What common instruction can be used to zero out a register?

Answer 4

XOR EAX, EAX (when EAX is the register that needs zeroing)

Question 5

Which instruction is used to increment a value?

Answer 5

INC op1

Question 6

Which instruction is used to decrement a value?

Answer 6

DEC op1

Question 7

What does the CMP instruction do? i.e CMP op1, op2

Answer 7

It compares the two specified operands and sets the appropriate EFLAGS values

Question 8

Which values are used to react to conditional jumps (i.e JZ, JE etc)

Answer 8

The EFLAGS values

Question 9

If a register is wrapped in square brackets, what does this mean? i.e [EAX]

Answer 9

[EAX] refers to the value stored at the memory address of EAX, not the value of EAX.