Architecture 06

Question 1

What are the key instruction groups?

Answer 1

• Data transfer (mov)
• Arithmetic (add, imul)
• Control flow (jumping to different place, ret)
• Logic (and, or, xor, not)
• Shift and rotate
• Comparisons (to set flags)
• ‘None of the above’
• Extensions

Question 2

What is meant by zero-extend?

Answer 2

When copying a short integer to a long integer, doubleword operations set higher 32 bits of 64 bit value to 0

Question 3

What is meant by sign-extend?

Answer 3

When copying a short integer to a long integer, some other mov instructions multiply the sign bit

Question 4

What is the ‘xchg’ instruction?

Answer 4

Instruction exchanges source and destination

Question 5

What is the ‘lea’ instruction?

Answer 5

“Load effective address” is like mov except that a computed address (rather than content of address) is put in the destination

Question 6

What is the difference between ‘mul’ and ‘imul’?

Answer 6

• ‘mul’ is unsigned
• ‘imul’ is signed
(Typically one operand involves rax)