AQA GCSE Computer Science 2027 Predicted Practice Paper — Paper 1

Answer ALL questions. Write your answers in the spaces provided. You must write down all the stages in your working.

Section A

Short-answer computational thinking questions. Answer ALL questions.

• 1

  Question SECTION-A1 (4 marks)

  A programmer is designing a system and uses abstraction and decomposition when planning it. (a) State what is meant by the term 'decomposition'. [1 mark] (b) State what is meant by the term 'abstraction'. [1 mark] (c) A vending machine returns change to a customer. Describe one detail that could be removed through abstraction when modelling this process, and explain why removing it is helpful. [2 marks]

  (Total for Question SECTION-A1 is 4 marks)
• 2

  Question SECTION-A2 (4 marks)

  Convert the denary (base-10) number 214 into: (a) an 8-bit binary number [2 marks] (b) a two-digit hexadecimal number [2 marks] Show your working.

  (Total for Question SECTION-A2 is 4 marks)
• 3

  Question SECTION-A3 (4 marks)

  A one-dimensional array called scores holds five integers using zero-based indexing: scores = [40, 12, 27, 63, 5] (a) State the value stored in scores[2]. [1 mark] (b) Write a single AQA-style pseudocode assignment statement that changes the last element of the array to 90 without using the literal index 4. [2 marks] (c) State one advantage of using an array rather than five separately named variables. [1 mark]

  (Total for Question SECTION-A3 is 4 marks)
• 4

  Question SECTION-A4 (4 marks)

  Consider the Boolean expression Q = (A AND NOT B) OR (NOT A AND B). (a) Complete a truth table for Q showing all four combinations of inputs A and B. [3 marks] (b) State the single common name for the logic gate that produces this output. [1 mark]

  (Total for Question SECTION-A4 is 4 marks)
• 5

  Question SECTION-A5 (5 marks)

  A programmer writes a subroutine that takes a whole number of pence and returns the number of complete 20-pence pieces it contains, ignoring any remainder. (a) Name the integer arithmetic operator that performs this whole-number division. [1 mark] (b) Name the operator that would instead give the remaining pence after taking out the 20p pieces. [1 mark] (c) Using both operators, show the two calculations and their results for an input of 97 pence. [3 marks]

  (Total for Question SECTION-A5 is 5 marks)
• 6

  Question SECTION-A6 (5 marks)

  A field-name text string is validated before being stored. The rule is: the string must be between 3 and 12 characters long (inclusive) and must not be empty. (a) Identify the type of validation check being described. [1 mark] (b) Give one example of a string that PASSES this check and one that FAILS, and state clearly which is which. [2 marks] (c) Explain the difference between validation and verification of data. [2 marks]

  (Total for Question SECTION-A6 is 5 marks)
• 7

  Question SECTION-A7 (5 marks)

  A large uncompressed sound file is 6 000 000 bytes in size. (a) Convert this size into megabytes (MB), using the convention that 1 MB = 1 000 000 bytes. [1 mark] (b) The file is compressed to 30% of its original size using a lossy compression method. Calculate the compressed file size in bytes. [2 marks] (c) State one advantage and one disadvantage of using lossy rather than lossless compression for this sound file. [2 marks]

  (Total for Question SECTION-A7 is 5 marks)
• 8

  Question SECTION-A8 (4 marks)

  A trace table is used to follow the execution of the pseudocode below. total <- 0 FOR i <- 1 TO 4 total <- total + (i * i) ENDFOR OUTPUT total (a) Complete a trace showing the value of total after each iteration of the loop. [3 marks] (b) State the value that is finally output. [1 mark]

  (Total for Question SECTION-A8 is 4 marks)

Section B

Programming and problem-solving. Answer ALL questions.

• 1

  Question SECTION-B1 (8 marks)

  A sports club stores its members' ages in a one-dimensional array called ages. The club wants a program that finds and outputs the age of the oldest member. (a) Write an AQA-style pseudocode algorithm that uses iteration to find the largest value in ages and outputs it. Assume the array contains at least one element and that a length function LEN(ages) is available. [6 marks] (b) Explain why your algorithm initialises the 'largest so far' variable to the first element of the array rather than to 0. [2 marks]

  (Total for Question SECTION-B1 is 8 marks)
• 2

  Question SECTION-B2 (9 marks)

  A program repeatedly asks the user to enter a password until they type the correct one, which is stored in a variable named secret. After three failed attempts the program locks and outputs 'Account locked'. On a correct entry it outputs 'Access granted'. Write an AQA-style pseudocode algorithm that implements this behaviour. Your solution should: - allow at most three attempts, - stop asking as soon as the correct password is entered, - output the correct message in each case. [9 marks]

  (Total for Question SECTION-B2 is 9 marks)
• 3

  Question SECTION-B3 (9 marks)

  A shop uses a program to work out the total cost of an order. A subroutine named priceOf(item) returns the price in pounds of a single item as a real number. An array called basket holds the names of the items a customer wants to buy. (a) Explain the difference between a subroutine that is a FUNCTION and one that is a PROCEDURE. [2 marks] (b) Write an AQA-style pseudocode FUNCTION called orderTotal that takes the basket array as a parameter, uses priceOf to look up each item's price, and returns the total cost of all items in the basket. Assume LEN(basket) gives the number of items. [7 marks]

  (Total for Question SECTION-B3 is 9 marks)
• 4

  Question SECTION-B4 (9 marks)

  A messaging app stores each contact's name and unread-message count. A programmer decides to use a linear search to find whether a given name appears in an array of contact names. (a) Describe how a linear search algorithm works. [3 marks] (b) The contact names happen to be stored in alphabetical order. State the name of a more efficient search algorithm that could be used, and explain in outline how it finds an item, referring to how the list is repeatedly divided. [5 marks] (c) State one situation in which a linear search would still be the better choice even though the data is sorted. [1 mark]

  (Total for Question SECTION-B4 is 9 marks)
• 5

  Question SECTION-B5 (10 marks)

  A school network is connected to the internet and stores pupils' personal data. (a) Describe what is meant by a 'brute-force attack' and state one measure that would make such an attack against user passwords less likely to succeed. [3 marks] (b) Explain how a firewall helps to protect the network. [2 marks] (c) The school also uses encryption for data sent across the network. Explain what encryption does and why it is useful even if an attacker manages to intercept the data. [3 marks] (d) A firewall on its own does not protect the network from every threat. Explain one further security measure the school should also use and why the firewall alone is not enough. [2 marks]

  (Total for Question SECTION-B5 is 10 marks)