17.2.2. Checking the Zero Flag

Try these first

1. 1.

   What does the zero flag indicate in a processor?

   Hint

   Think about what happens during addition or subtraction.

2. 2.

   What is the function of a jump instruction?

   Hint

   Consider how programs make decisions.

3. 3.

   What does the zero flag signify in processor operations?

   • The last operation was successful
   • The last operation resulted in zero
   • The last operation failed

   Hint

   Identify what the zero flag specifically checks.

4. 4.

   True or False: An unconditional jump instruction always checks the zero flag.

   • True
   • False

   Hint

   Consider the behavior of unconditional versus conditional jumps.

5. 5.

   Design a simple assembly loop that decrements a value and uses the zero flag to exit the loop. Explain the role of the zero flag in this context.

   Hint

   Write out the loop and use comments to clarify the significance of the zero flag.

6. 6.

   Discuss the implications of using an incorrect flag condition in a jump instruction. How might it affect program execution?

   Hint

   Think through the flow control consequences when the condition check fails.