Practise Computational thinking. 12 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Written for this site in the style of OCR exam questions. They are not taken from real past papers.
Question 1Easy3 marks
(a) Which statement best describes abstraction? Tick (✓) one box.[1]
Breaking a problem down into smaller sub-problems
Removing unnecessary detail so that only the important parts of a problem are considered
Writing the steps needed to solve a problem in a logical order
Checking that a program works using a range of test data
(b) State what is meant by decomposition.[1]
(c) Give one benefit of decomposing a problem before writing a program.[1]
Show the answer and mark scheme
(a)Answer: Removing unnecessary detail so that only the important parts of a problem are considered
(b)
breaking a (complex) problem down into smaller (more manageable) sub-problems / parts / tasks
(c)
each sub-problem is simpler / easier to understand, code or test
different sub-problems can be worked on by different programmers (at the same time)
the sub-programs produced can be reused (in this or other programs)
errors are easier to find / the program is easier to maintain
Question 2Medium5 marks
A leisure centre wants a program that lets members book places on fitness classes online. The programmer uses decomposition to plan the program.
(a) Identify three sub-problems that the programmer could split this problem into.[3]
(b) Explain one way in which decomposition will help the programmer.[2]
Show the answer and mark scheme
(a)
logging in / checking the member's username and password
displaying the timetable / list of classes
checking whether a class has spaces left
recording / saving a booking
taking payment
sending a confirmation (email / message) to the member
cancelling a booking
(b)
a benefit, e.g. each sub-problem is smaller / simpler / can be tackled one at a time / can be given to different programmers / can be tested separately
linked explanation, e.g. so the program is quicker / easier to write / so errors are easier to locate and fix / so modules can be reused
Question 3Hard6 marks
A city council wants a computer model to try out different timings for the traffic lights at a busy crossroads before it changes the real lights.
(a) Describe how abstraction could be used when creating the model.[3]
(b) Describe how decomposition could be used when creating the model.[3]
Show the answer and mark scheme
(a)
remove details that do not affect the flow of traffic, e.g. the make / colour of the cars, drivers' names, nearby buildings
keep the details that do affect the flow of traffic, e.g. number of vehicles arriving per minute, light timings, number of lanes
represent vehicles simply, e.g. as a number in a queue / all the same size and speed
this makes the model simpler / quicker to create / quicker to run
but enough detail must be kept for the results to be realistic / useful
(b)
split the model into smaller parts / modules / sub-programs
identifies a suitable part, e.g. controlling the sequence of the lights / generating arriving vehicles
identifies a second suitable part, e.g. moving vehicles through the junction / recording queue lengths or waiting times
each part can be developed / tested separately / by different people
parts can be broken down further until each one is easy to solve
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