Variables, constants, input, output and assignment

OCR GCSE Computer Science (J277) · Algorithms and programming (Paper 2) › Programming fundamentals › Programming fundamentals

Practise Variables, constants, input, output and assignment. 12 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.

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Look at this program. 01 const VAT = 0.2 02 price = float(input("Enter price")) 03 total = price + price * VAT 04 print(total) Identify the constant used in the program.: VAT
Look at this program. 01 name = input("What is your name?") 02 age = int(input("How old are you?")) 03 age = age + 1 04 print("Next year " + name + " will be " + str(age)) State the output if the user enters Sam and then 14.: Next year Sam will be 15
Look at this program. 01 name = input("Enter your name") 02 const GREETING = "Welcome" 03 print(GREETING + ", " + name) Identify the constant used in the program.: GREETING

Sample questions

Written for this site in the style of OCR exam questions. They are not taken from real past papers.

Question 1Easy4 marks

Look at this program.

01 const VAT = 0.2
02 price = float(input("Enter price"))
03 total = price + price * VAT
04 print(total)

(a) State what is meant by a variable.[1]

(b) State what is meant by a constant.[1]

(d) Identify the line number of the line that outputs data.[1]

Show the answer and mark scheme

(a)

a named location in memory that stores a value that can change while the program is running

(b)

a named value that cannot change while the program is running

(d) Answer: 04

04 / line 4

Question 2Medium5 marks

A gym uses this program to work out the cost of a membership.

01 const MONTHLY_FEE = 25
02 months = int(input("Number of months"))
03 cost = MONTHLY_FEE * months
04 if months >= 12 then
05    cost = cost - 30
06 endif
07 print(cost)

(a) State the output when the user enters 12.[1]

(b) Explain why MONTHLY_FEE has been declared as a constant rather than as a variable.[2]

(d) A programmer adds the line MONTHLY_FEE = 30 near the end of the program. Explain what would happen.[1]

Show the answer and mark scheme

(a) Answer: 270

(b)

its value does not need to change while the program runs / it cannot be changed by mistake
if the fee changes, it only needs to be updated in one place, making the program easier to maintain

(c)

30 (the discount) / 12 (the number of months needed for the discount)

(d)

an error would be reported / the program would not run, because the value of a constant cannot be changed

Question 3Hard7 marks

This program should work out the interest earned on a savings account. It contains two errors.

01 const RATE = 0.05
02 balance = float(input("Enter balance"))
03 years = int(input("Enter years"))
04 for y = 1 to years
05    interest = balance * RATE
06    balance = balance + interest
07 next y
08 RATE = 0.06
09 print("Final balance: " + str(balance))
10 print("Total interest: " + str(totalInterest))

(a) Identify the two errors in the program and explain why each one is an error.[4]

(b) Describe the changes needed so that line 10 outputs the total interest earned.[2]

Show the answer and mark scheme

(a)

line 08
the value of a constant cannot be changed while the program is running
line 10
totalInterest is used but has never been declared / given a value

(b)

set totalInterest to 0 before the loop
inside the loop, add interest to totalInterest (totalInterest = totalInterest + interest)

Final balance: 1102.5

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