Computer Science 52 marks
11 / 1
State what is meant by the term algorithm.
algorithm means a set of instrusions the things will follow
1 min on this question
Got it: instructions that are followed. In the exam add what they are for — a task or a problem — to make it watertight.
20 / 1
State what is meant by decomposition in computational thinking.
taking the code apart
1 min on this question
Decomposition is about a problem, not code. Think: what do you do to a big problem to make it easier to start?
30 / 1
State what is meant by abstraction in computational thinking.
a different way of using code
1 min on this question
Abstraction is about detail: which detail do you keep and which do you leave out when you describe a problem?
40 / 3
State the most appropriate data type for each of the following values in a program.
- The number of pupils in a class.
- The average height of the pupils, in metres.
- Whether or not a pupil has paid for the trip.
1. list
2. list
3. probibilty
q
2 min on this question
The five data types have names (whole numbers, decimals, text, true/false, a single character). Which of those fits each value?
52 / 2
State the value of each expression in Python 3.
17 // 517 % 5
1. 3
2. 2
1 min on this question
Both right — integer division and remainder, cold, after last week's teaching. Keep it.
62 / 2
State the output of each Python 3 statement.
print("4" + "5")print(int("4") + int("5"))
1. the outcome is 45
2. the outcome is 9
1 min on this question
Both right — text joins, int() adds. The exact thing you got wrong last week, now correct without notes.
70 / 2
State the output of this Python 3 program.
for i in range(2, 9, 3):
print(i)
2, 3, 4, 5, 6, 7, 8, 8, 7, 6, 5, 4
1 min on this question
range has three numbers here: start, stop, step. The third one is the jump between values. Trace it one value at a time.
80 / 3
A program contains the variables x = 7 and y = 3.
State whether each condition is True or False.
x > 5 and y > 5not (x == y)x < 10 or y < 1
1. x is true and y is false
2. false
3. x is true and y is false
2 min on this question
You checked each half — good start — but the question wants one final True or False. What does and need from both halves? What does or need? What does not do to an answer?
92 / 3
A cinema charges for tickets by age:
- under 5: free
- 5 to 15 inclusive: £3
- 16 and over: £5
The variable age already holds a whole number.
Write a Python 3 program that uses age to store the correct price in a variable called price.
age = int(input())
if age < 5:
print("Free")
elif age < 16:
print("£3")
else:
print("£5")
6 min on this question
Your bands and boundaries are all right — that's the hard part. Read the task again: it asked you to STORE the price in a variable called price, not display it, and age was already set.
103 / 3
Write a Python 3 program that keeps asking the user to enter a password until they enter open. When they do, the program should display Welcome.
password = input()
while password != open
print("Please try agian")
password = input()
print("Welcome")
4 min on this question
Full marks on the logic — loop, input inside, Welcome after. One thing to fix in your habits: the word you're comparing against is text, and text needs quote marks. And the colon.
112 / 4
Complete a trace table for this Python 3 program. Type one row for each time a value changes, with the columns a and b, and then state the output.
a = 5
b = 2
while a > 0:
a = a - b
b = b + 1
print(a)
a = 3
b = 3
a = 0
b = 4
-1
a = 3
b = 3
a = 0
b = 4
2 min on this question
Your two loop rows were exactly right. Two things: a trace table starts with the values BEFORE the loop, and it stops the moment the while condition is false — check a > 0 before doing another pass.
120 / 3
A program contains this array (list):
scores = [12, 7, 9, 15]
- State the value of
scores[2]. - Write one statement that changes the value 7 to 8.
- Write one statement that displays how many items are in the array.
1. 7
2.i don't know
3. count items in scores
3 min on this question
Lists count from 0, not 1 — so the first item is position 0. You'll be taught how to change one item and how to ask a list how long it is; not yet covered, so nothing to worry about.
130 / 2
A program contains this two-dimensional array:
grid = [[1, 2, 3], [4, 5, 6]]
- State the value of
grid[1][0]. - State the value of
grid[0][2].
1. 1
2. 5
1 min on this question
A 2-D list is a list of lists: the first number picks the row, the second picks the item in that row, both counting from 0. Not taught yet.
140 / 3
A program contains:
name = "Paddington"
first = "Paige"
last = "Mann"
- State the value of
len(name). - State the value of
name[0:3]. - Write an expression that joins
first and last with a single space between them.
1. paddington
2. paddington
3. print("{first} {last}")
1. paddington
2. paddington
3. print("{first} {last}")
2 min on this question
len() gives a number (how many characters), and [0:3] picks out a piece of the text. Not taught yet — it's coming.
152 / 2
In Python 3, ord("A") returns 65.
- State the value of
ord("D"). - State the value of
chr(67).
1. 68
2. C
2 min on this question
Both right — you reasoned from A = 65 without being told how. Nice.
160 / 1
Write one line of Python 3 that stores a random whole number from 1 to 6 (inclusive) in a variable called dice. You may assume import random has already been done.
dice = while i in range (1, 7)
1 min on this question
This wanted a function from the random module, not a loop. Not taught yet.
170 / 4
- Write a Python 3 subroutine (function) called
area that takes two parameters, width and height, and returns the area of a rectangle. - Write one line that calls
area with the values 4 and 5 and stores the result in a variable called a.
width = int(input())
height = int(input())
a = width*height
width = int(input())
height = int(input())
a = width*height
2 min on this question
The multiplication is right, but a subroutine is a named block you define once and call later with values — a different shape of code you haven't been taught yet.
180 / 3
A program accepts a pupil's age, which must be a whole number from 11 to 18 inclusive.
Give one item of test data for each type below, and state what the program should do with it.
- Normal
- Boundary
- Erroneous
1. 15
2. 18
3. 10
3 min on this question
All three of your values are in the right class — that's the knowledge. The question also asked what the program SHOULD DO with each one (accept it / reject it), and each mark needed both halves. Read the whole question.
192 / 2
This program should display the average of four test scores.
total = 45 + 62 + 58 + 71
average = total / 3
prnt(average)
The program contains one syntax error and one logic error.
- State the line that contains the syntax error and what is wrong with it.
- State the line that contains the logic error and what is wrong with it.
1. syntax error is on line 3 because the i is missing in print
2. logic error is on line 2 and it is the 3 because it should be a 4
3 min on this question
Both right, with the line number and the reason — exactly how the exam wants it.
200 / 2
A binary search is used to find the value 27 in this list:
3, 8, 12, 15, 21, 27, 30
- State the values that are compared, in the order they are checked, until 27 is found.
- State one reason a binary search could not be used if the list were not sorted.
1. 3 == 27 = false, 8 == 27 = false, 12 == 27 = false, 21 == 27 = false, 27 == 27 = true
3 min on this question
You checked the items one by one from the start — that's a linear search. A binary search jumps to the middle first. Part 2 was left empty: always write one sentence.
212 / 3
A bubble sort is used to sort this list into ascending order:
5, 1, 4, 2
- Show the list after the first pass.
- State how the algorithm knows the list is fully sorted.
1. 1, 4, 2, 5
2. it checks the list and finds it sorted
2 min on this question
First pass perfect. For part 2 be precise: what has to happen in a whole pass for the sort to know it can stop?
221 / 2
Describe the two main stages of a merge sort.
using merge sort splits the list into multipule peaks and puts them together after sorting them
3 min on this question
You've got the two stages in the right order. Say how far the splitting goes, and that the ordering happens during the joining, not before it.
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