Designing algorithms — GCSE Computer Science practice questions

Question 1

Priya is writing a bus-timetable app for her school. She has already found out exactly what the app must do. She is now drawing a structure diagram of the app and writing its main steps in pseudocode.

Which stage of the program development life cycle is she working on?

Accepted Answer

B: Design. Structure diagrams, flowcharts and pseudocode are produced in the design stage, which plans how the solution will work. Finding out what the app must do was the analysis stage, which she has finished. Coding is writing the program in a programming language, and testing checks the finished program.

Question 2

A developer is designing a route-planning app for cyclists in Lisbon.

Which of these is an example of abstraction?

Accepted Answer

B: Showing only roads, cycle lanes and hills on the map, and leaving out the colours and shapes of buildings. Abstraction means removing the details that are not needed to solve the problem, so the map keeps only what a cyclist needs (roads, cycle lanes, hills) and leaves out building colours and shapes. Splitting the app into parts is decomposition; adding every shop name adds detail instead of removing it; checking a long route is testing.

Question 3

A go-kart club times six drivers over one lap of its track. Each time is in seconds and is less than 99. Fig. 1 shows the flowchart of the program used by the coach.

What is the purpose of the flowchart?

Accepted Answer

B: To output the number of the driver with the fastest (lowest) time. The loop inputs six times. Whenever a time is lower than the best so far, Best takes that time and Winner takes the driver's number. At the end only Winner is output, so the flowchart outputs the number of the driver with the lowest (fastest) time.