Final answer:
The TestAndSet instruction is executed atomically to prevent race conditions by ensuring that the operation is indivisible and no other process can interfere.
Step-by-step explanation:
The TestAndSet instruction is executed atomically. This means that it is completed as a single, indivisible operation to ensure that no other processes can access the variable being tested and set until the operation is finished. The purpose of an atomic operation is to prevent race conditions in concurrent programming, where multiple processes or threads access shared data concurrently. Atomic operations are critical for implementing locks and synchronization mechanisms in computer systems.