AQA AS Computer Science Paper 1 2025 | 7516/1 Questions & Mark Scheme

AS
COMPUTER SCIENCE
Paper 1


Tuesday 13 May 2025 Afternoon Time allowed: 1 hour 45 minutes
Materials
For this paper you must have:
• a computer
• a printer
• appropriate software
• the Electronic Answer Document
• an electronic version and a hard copy of the Skeleton Program
• an electronic version and a hard copy of the Preliminary Material
• an electronic version of the Data Files MapData.txt and HiddenData.txt
You must not use a calculator.

Instructions
• Type the information required on the front of your Electronic Answer Document.
• Before the start of the examination make sure your Centre Number, Candidate Name and
Candidate Number are shown clearly in the footer of every page (not the front cover) of your
Electronic Answer Document.
• Enter your answers into the Electronic Answer Document.
• Answer all questions.
• Save your work at regular intervals.

Information
• The marks for questions are shown in brackets.
• The maximum mark for this paper is 75.
• No extra time is allowed for printing and collating.
• The Question Paper is divided into three sections.

Advice
You are advised to allocate time to each section as follows:
Section A – 20 minutes; Section B – 25 minutes; Section C – 60 minutes.

At the end of the examination
Tie together all your printed Electronic Answer Document pages and hand them to the Invigilator.

Warning
It may not be possible to issue a result for this paper if your details are not on every page of your
Electronic Answer Document.




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, 2


Section A

You are advised to spend no more than 20 minutes on this section.

Enter your answers to Section A in your Electronic Answer Document. You must save this
document at regular intervals.

Question 03 in this section asks you to write program code starting from a new
program/project/file.

You are advised to save your program at regular intervals.


0 1 Figure 1 shows the data structures Letter, L and R used by the algorithm shown
in Figure 2.

Figure 1

Letter L R
[0] [0] 5 [0] 20
[1] A [1] 18 [1] 23
[2] B [2] -1 [2] -1
[3] C [3] -1 [3] -1
[4] D [4] 2 [4] 24
[5] E [5] 9 [5] 1
[6] F [6] -1 [6] -1
[7] G [7] 26 [7] 17
[8] H [8] -1 [8] -1
[9] I [9] 19 [9] 21
[10] J [10] -1 [10] -1
[11] K [11] 3 [11] 25
[12] L [12] -1 [12] -1
[13] M [13] 7 [13] 15
[14] N [14] 4 [14] 11
[15] O [15] -1 [15] -1
[16] P [16] -1 [16] -1
[17] Q [17] -1 [17] -1
[18] R [18] 12 [18] -1
[19] S [19] 8 [19] 22
[20] T [20] 14 [20] 13
[21] U [21] 6 [21] -1
[22] V [22] -1 [22] -1
[23] W [23] 16 [23] 10
[24] X [24] -1 [24] -1
[25] Y [25] -1 [25] -1
[26] Z [26] -1 [26] -1




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, 3


Figure 2

M ← "1001"
Current ← 0
FOR i ← 0 TO 3
Symbol ← M[i]
IF Symbol = "0" THEN
Current ← L[Current]
ELSE
Current ← R[Current]
ENDIF
ENDFOR
OUTPUT Letter[Current]

Complete Table 1 by hand-tracing the algorithm in Figure 2.

The strings are zero index based. For example, the character with index 0 in the
string "ABCD" is "A".

You may not need to use all the rows in Table 1.

The first row of Table 1 has already been completed for you.

Table 1


M i Symbol Current Output

"1001" 0




Copy the contents of all the unshaded cells in Table 1 into your Electronic
Answer Document.
[3 marks]


Turn over for the next question




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, 4


0 2 Figure 3 and Figure 4 show two blocks of pseudo-code.

Figure 3

INPUT X
WHILE X > 0
X ← X – 1
ENDWHILE

Figure 4

INPUT X
REPEAT
X ← X – 1
UNTIL X ≤ 0


Explain why the pseudo-code in Figure 3 operates differently to the pseudo-code in
Figure 4 when the inputs are negative numbers.
[2 marks]


0 3 Figure 5 shows an algorithm represented using pseudo-code.

Figure 5

S ← ""
WHILE S ≠ "x"
OUTPUT "Enter a word or phrase: "
INPUT S
Max ← LENGTH(S) – 1
Matched ← True
FOR i ← 0 TO Max
Letter1 ← S[i]
Letter2 ← S[Max - i]
IF Letter1 ≠ Letter2 THEN
Matched ← False
ENDIF
ENDFOR
IF Matched = True THEN
OUTPUT "Palindrome"
ELSE
OUTPUT "Not a palindrome"
ENDIF
ENDWHILE

The strings are zero index based. For example, the character with index 0 in the
string "ABCD" is "A".




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