Question Number 1 [4+4]:

1. The philosophy of Cleanroom Software Engineering focuses on defect removal rather than defect avoidance, explain its advantages. Describe the Cleanroom Software Engineering Strategy, and also explain the importance of statistical usage testing used in cleanroom software development.
2. Why traditional testing insufficient for safety critical systems? Discuss the role of MODEL CHECKING in the field of software verification for safety critical systems. Consider the following digital circuit with given condition: y=NOT(XOR(x,r)) and r_(next)= XOR(x,r). Apply model checking to verify the circuit at different input values [start with x=1 and r=0]

XOR NOT -y r register