This book describes current software-engineering methods for writing (nearly) bug-free programs. These methods are based on practices developed at IBM and elsewhere under the name Cleanroom Software Engineering. In a concise presentation, the author shows how to apply these methods in three key areas of software development: specification, verification, and testing. Requiring formal specifications forces programmers to program more simply and more clearly, eliminating many defects as a consequence. Performing semiformal verification as part of a team process uncovers additional defects. Testing the program, to compensate for human fallibility in the preceding steps, catches (nearly) all remaining bugs. The author departs somewhat from IBM Cleanroom methods to simplify the formalism that programmers must learn, and to make specification and verification readily accessible to anyone who can write well-structured programs. Although the book's examples are written in several programming languages, the largest number is in C.