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Subjects · Leaving Cert Computer Science

Leaving Cert Computer Science: Abstraction & pattern recognition

How often Abstraction & pattern recognition comes up on the Computer Science papers, every year it was asked, and questions to try.

HL Asked on 5 of the last 5 Higher Level papers, most recently in 2025. banker

OL Asked on 3 of the last 5 Ordinary Level papers, most recently in 2025. most years

Abstraction & pattern recognition, Higher Level(6 marks)

Quick ones on Abstraction & pattern recognition.

(a)What is abstraction in computational thinking?
  1. Breaking a problem into smaller parts to solve each one
  2. Removing unneeded detail to focus on what matters
  3. Spotting what several problems have in common to reuse
(b)What is decomposition?
  1. Finding similarities between problems to reuse solutions
  2. Hiding unnecessary detail so only the key facts remain
  3. Breaking a problem into smaller, manageable parts
(c)What is pattern recognition in computational thinking?
  1. Spotting similarities or trends in problems or data
  2. Choosing test data at the boundaries of valid ranges
  3. Removing unneeded detail from a problem to simplify it
Show the answers

(a) Removing unneeded detail to focus on what matters

(b) Breaking a problem into smaller, manageable parts

(c) Spotting similarities or trends in problems or data

Your turn: Higher Level questions on Abstraction & pattern recognition.

Higher Level

Asked on 5 of the last 5 Higher Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2025B15
2024A11
2023A8, B13
2022A10, A11
2021B14

Links open the State Examinations Commission’s paper for that year.

More Abstraction & pattern recognition questions

Abstraction & pattern recognition, 3 marks

What is the 6th term of 2, 6, 18, 54, ...?

  1. 162
  2. 108
  3. 486
Show the answer

486

Each term is 3 times the one before: 2, 6, 18, 54, 162, 486. 162 is only the 5th term. The nth term is 2 * 3 ** (n - 1).

Abstraction & pattern recognition, 3 marks

What is 1 + 2 + 4 + 8 + ... + 128?

  1. 128
  2. 255
  3. 256
Show the answer

255

Adding the powers of 2 up to 128 always gives one less than the next power: 256 - 1 = 255. It is also the largest 8-bit value, 11111111.

Abstraction & pattern recognition, 3 marks

What is the last digit of 7 ** 100?

  1. 1
  2. 7
  3. 9
Show the answer

1

The last digits of powers of 7 repeat 7, 9, 3, 1 every 4 powers. 100 is a multiple of 4, so 7 ** 100 ends like 7 ** 4 = 2401, in 1.

Ordinary Level

Asked on 3 of the last 5 Ordinary Level papers, most recently in 2025. most years

Every paper, year by year

YearWhere it came up
2025A7
2024Not asked
2023A5
2022B14
2021Not asked

Links open the State Examinations Commission’s paper for that year.

More Abstraction & pattern recognition questions

Abstraction & pattern recognition, 2 marks

Hiding details that are not needed so you can focus on what matters is called…

  1. Decomposition
  2. Iteration
  3. Abstraction
Show the answer

Abstraction

Abstraction keeps only what the task needs. A car in a racing game needs a speed and a position, not the colour of its seats.

Abstraction & pattern recognition, 2 marks

Breaking a big problem into smaller parts that are easier to solve is called…

  1. Encryption
  2. Decomposition
  3. Abstraction
Show the answer

Decomposition

Decomposition splits a task into parts, e.g. a quiz app into questions, scoring and a results screen. Each part can be built and tested on its own.

Abstraction & pattern recognition, 2 marks

Next number in the pattern 3, 7, 11, 15, …?

  1. 19
  2. 18
  3. 21
Show the answer

19

The rule is add 4 each time: 15 + 4 = 19. Spotting a rule like this is pattern recognition, and a rule can be turned into a loop.

Other Computer Science topics

All of Leaving Cert Computer Science