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Leaving Cert Computer Science: Turing machines

How often Turing machines comes up on the Computer Science papers, every year it was asked, and questions to try.

HL Asked on 1 of the last 5 Higher Level papers, most recently in 2022.

Turing machines, Higher Level(8 marks)

Quick ones on Turing machines.

(a)What does a Turing machine read and write symbols on?
  1. A hard disk
  2. An infinitely long tape
  3. A deck of punched cards
(b)What decides a Turing machine's next action?
  1. Input typed in by a user at a keyboard
  2. Its clock speed and the length of its tape
  3. Its current state and the symbol it reads
(c)Why is the Turing machine important in computer science?
  1. It is a simple model of what any computer can compute
  2. It cracked the Enigma code on its own during the war
  3. It was the first commercial computer sold to businesses
Show the answers

(a) An infinitely long tape

(b) Its current state and the symbol it reads

(c) It is a simple model of what any computer can compute

Your turn: Higher Level questions on Turing machines.

Higher Level

Asked on 1 of the last 5 Higher Level papers, most recently in 2022.

Every paper, year by year

YearWhere it came up
2025Not asked
2024Not asked
2023Not asked
2022A12
2021Not asked

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

More Turing machines questions

Turing machines, 3 marks

What is a universal Turing machine?

  1. One that needs no tape to store its symbols
  2. One that can only add and subtract numbers
  3. One that can simulate any other Turing machine
Show the answer

One that can simulate any other Turing machine

Given a description of another machine on its tape, it can carry out that machine's work. This is the idea behind the stored-program computer.

Turing machines, 3 marks

What did Turing show about the halting problem?

  1. Loops can be removed from any program to make sure it stops
  2. No program can decide for every program if it will stop
  3. Every program eventually stops if it is left to run
Show the answer

No program can decide for every program if it will stop

In 1936 Turing proved there is no general method to tell, for any program and input, whether it halts or runs forever. Some problems cannot be computed.

Other Computer Science topics

All of Leaving Cert Computer Science