Arrays, records and SQL – GCSE Computer Science exam questions with mark scheme

1Grade 6–76 marks

A weather station records 10 temperatures each day.

Write a program that:

• asks the user to enter 10 temperatures and stores them in an array

• calculates and outputs the mean temperature

• outputs how many temperatures are above 20.

Use OCR Exam Reference Language or a high-level programming language. [6]

Declares / initialises an array or list to hold the temperatures, e.g. array temps[10]; allow temps = [] with append in Python(1)
Uses a loop that runs exactly 10 times to input values (e.g. for i = 0 to 9; for i in range(10)); allow a condition-controlled loop with a counter that is correctly updated so it runs 10 times(1)
Stores each input in the array (at the loop index or by append); ignore whether or not the input is cast to real/int(1)
Calculates the mean correctly: running total (or sum of the array) divided by 10 / the array length(1)
Counts the values strictly greater than 20; allow in the same loop or a separate loop(1)
Outputs both the mean and the count, once each (after the loop)(1)

Answer:

array temps[10]
total = 0
above = 0
for i = 0 to 9
    temps[i] = float(input("Enter temperature"))
    total = total + temps[i]
    if temps[i] > 20 then
        above = above + 1
    endif
next i
print("Mean: " + str(total / 10))
print("Above 20: " + str(above))

Examiner tip: 'Above 20' means > 20, not >= 20. Also, the outputs go after the loop, or they will be printed ten times.

2Grade 4–54 marks

A database table called Pupils is shown.

PupilID	FirstName	Surname	Year	Points
1	Amir	Khan	10	64
2	Bella	Hughes	11	45
3	Chen	Li	10	38
4	Dara	Okafor	11	72
5	Ella	Patel	10	55

(a) Write an SQL statement to display the FirstName and Points of every pupil in Year 11. [3]

(b) State the output of this SQL statement:

SELECT Surname FROM Pupils WHERE Year = 10 AND Points > 50

[1]

SELECT FirstName, Points(1)
FROM Pupils(1)
WHERE Year = 11(1)
Khan and Patel (both needed, nothing else)(1)
Answer: (a) SELECT FirstName, Points FROM Pupils WHERE Year = 11; (b) Khan, Patel
Examiner tip: Name the exact fields after SELECT. Writing SELECT * loses the first mark when the question asks for specific fields.

3Grade 6–76 marks

A 2D array marks stores test marks for 3 students (rows 0–2) in 4 tests (columns 0–3). marks[student, test] is used to access a value.

	Test 0	Test 1	Test 2	Test 3
Student 0	12	15	9	18
Student 1	7	14	20	11
Student 2	16	10	13	19

(a) State the value of marks[1, 2]. [1]

(b) Write code that calculates and outputs the total mark for each student. Use OCR Exam Reference Language or a high-level programming language. [5]

(a) 20(1)
(b) Outer loop through the 3 students (0 to 2)(1)
(b) Total reset to 0 for each student (inside the outer loop, before the inner loop); allow a total built fresh for each student, e.g. Python sum(marks[s])(1)
(b) Inner loop through the 4 tests (0 to 3); allow sum(marks[s]) / sum of the row in place of the inner loop(1)
(b) Adds marks[student, test] to the total with indexes the right way round (so each total is a student's row, not a test's column); allow Python marks[s][t]; allow sum(marks[s]) / sum of the student's row(1)
(b) Outputs each student's total after the inner loop (giving 54, 52, 58)(1)

Answer: (a) 20; (b) nested loops output totals 54, 52, 58

for s = 0 to 2
    total = 0
    for t = 0 to 3
        total = total + marks[s, t]
    next t
    print("Student " + str(s) + ": " + str(total))
next s

Examiner tip: Reset the total inside the outer loop. If you don't, each student's total carries on from the one before.

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