Computer Architecture

Question 1

What is the two’s compliment number representation?

Answer 1

It is the most common format used to represent signed integers in modern computers.
A positive integer in two’s complement always has a 0 in the leftmost bit (sign bit) and is represented the same way as an unsigned binary integer.
To negate a number we invert all the bits and add one.

Question 2

What is two’s compliment of 0 (zero)?

Answer 2

0000 -> 1111 (inversion)
1111 + 1 -> 0000 (overflow is discarded)
Answer: 0

Question 3

Given a negative number in two’s compliment form how to convert it to a human understandable form?

Answer 3

1. Inverse the given binary number in two’s compliment
2. Add 1 to the result of inversion
3. Add minus sign to the result.

Question 4

What is the range of number which can be represented by 8-bit binary in 2’s compliment format?

Answer 4

• 2^7 … (2^7) -1, or
  -128 … 127
  That is because +128 and -128 cannot be represented by the same pattern, 1000 0000. The best option for 1000 0000 is to represent -128

Question 5

Convention steps of calling procedure on 32-bit architecture?

Answer 5

Caller:

• put calling procedure arguments on the stack
• put procedure return address on the stack

Callee:

• put previous base pointer address on the stack
• sync base pointer with the current stack pointer
• save CPU registers the callee procedure may modify in the stack