2.3. Examples of Flag Usage in Control Instructions

Try these first

1. 1.

   What flag indicates that an arithmetic result is zero?

   Hint

   Think about what signifies a total absence of value.

2. 2.

   In what condition is the overflow flag set?

   Hint

   Consider cases where numbers go beyond their limits.

3. 3.

   What does the overflow flag indicate?

   • The result is zero
   • The result is negative
   • The result exceeds data type limit

   Hint

   Focus on the scenarios where result values cannot fit.

4. 4.

   True or False: The carry flag is relevant in signed arithmetic.

   • True
   • False

   Hint

   Think about the goals of signed versus unsigned arithmetic.

5. 5.

   You have two signed 4-bit numbers: 0111 (7 in decimal) and 1001 (-7). Add them, and describe the resulting flags.

   Hint

   Focus on the outcome of the addition and its effects on the state of the flags.

6. 6.

   During an addition of 1001 (-7 in two's complement) and 1000 (-8), an overflow occurs. Discuss the implications and which flags are affected.

   Hint

   Reflect on what happens when operations yield unexpected results due to limits.