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AS 1 Introduction to Object Oriented Development
Quick questions on Control structures: sequence, selection and iteration - CCEA A-Level Software Systems Development
6short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is sequence?Show answer
Sequence alone can solve only fixed, linear problems. Order matters: swapping two statements can change the result, for example you must read a value before you use it.
What is selection?Show answer
Selection chooses between alternative paths according to a condition. The if statement is the main form, with optional else and else if branches; the case (or switch) statement is a tidy way to choose among many fixed values of one variable.
What are off-by-one and boundary errors?Show answer
>= 40 includes 40, but > 40 does not. Loop bounds matter too: for i = 1 to 10 runs 10 times, but for i = 0 to 10 runs 11. Check the boundaries.
What are infinite loops?Show answer
An indefinite loop whose condition never becomes false (the controlling variable is never updated) runs forever. Always change the controlling value inside the loop.
What is q1?Show answer
Name the three basic control structures. [3 marks]
What is q2?Show answer
State whether a while loop or a repeat until loop is guaranteed to execute its body at least once, and explain why. [2 marks]
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