A Level Computer Science OCR Practice Exam

What does the "BRP" instruction check for before branching?

1. Whether the accumulator is zero

2. Whether the accumulator is negative

3. Whether the accumulator is positive or zero

4. Whether the accumulator is full

The correct answer is: Whether the accumulator is positive or zero

The "BRP" instruction stands for "Branch if Positive." This instruction checks the value in the accumulator and determines whether it is positive or zero. If the accumulator contains a positive value or zero, the instruction will cause the program to branch to a specified address. This is essential in control flow because it allows the program to direct its execution based on the state of the accumulator at that moment. The focus on positive or zero values is crucial for various algorithms where the continuation of a loop or the execution of a sequence of instructions is conditional upon non-negative values. The ability to branch based on these conditions enables more sophisticated control structures in programming. Understanding this condition is vital, especially in programming environments where error handling and control flow based on numerical computations are common. It allows for the creation of programs that can respond dynamically to changing data and conditions.