1. Starter 15//2 = 7 (Quotient or Floor) (Modulus) 22%3 =1
State the values that would be stored in the variable “result”.
(a) Result = 15 DIV 2
15//2 = 7
(Quotient or Floor)
(Modulus)
22%3 =1
(b) Result = 22 MOD 3
(Exponent or power)
3**3 = 27
(c) Result = 3^3

2. true false true 2 For the following, X = 3 and Y = 6.
(a) State whether the following statements are true or false:
(i) X = Y/2
(ii) X > Y
(iii) Y <= X*2
true
false
true

3. X = 3 and Y = 6.
State what would be output from the following algorithm:
(i) If (X > 2 AND Y < 5)
print (“true”)
else
print (“false”)
endif
false

4. true false X = 3 and Y = 6. (ii) If the first line states:
If (X > 2 OR Y < 5)
(iii) If the first line states:
If NOT (X < 4 OR Y < 5)
true
false

6. GCSE Computer Science
Algorithms
Revision

7. Abstraction Some examples Real life Abstraction Your School day
A way of looking at a real-life thing that helps us to think more clearly about it.
Some examples
Real life
Abstraction
Your School day
Your time table

8. Abstraction
Abstraction is the method of removing the unnecessary details and include only the relevant details in order to solve a problem.

9. Lets imagine you are creating an interface for a Satnav.
How would you apply abstraction?

12. 7 9 A B 1 F 2 7 E 1 2 G H 8 3 C D

13. 7 9 A B 1 F 2 7 E 1 2 G H 8 3 C D

14. Input or Output
Decision
Input or Output
Stop

15. Challenges Then print the result of the calculation
1) Write a python program that inputs 2 numbers and a + - * /
Then print the result of the calculation
2) Write a Python program to input 4 numbers then calculate and print the average
3) Write a Python program to input a list of n numbers and print the average (while loop)

16. Abstraction of code…
When we code our program a flowchart is technically an “abstraction” of our algorithm and the code we write.

19. Thinking about the data
We can use abstraction to visualise the data structure.
We can store this data in 2 dimensional array (List)

20. We know we want to search each row in the grid.
A FOR loop suits this perfectly.

21. Decomposition Get the paddle to interact with the user
Validation on paddle. Don’t want to go off the screen
Draw the ball
Add sound
Get Ball to bounce
Add better graphics
Draw the tiles
Add special effects
Get the ball to detect when its hit a tile
Add in game winning and losing conditions

22. Block Diagram Development
Ball Small
Get paddle to display
Draw the ball
Draw the tiles
Play sounds
Manage score
Draw paddle in pixels and display
Get Ball to bounce
Remove hit tiles
Monitor win/lose conditions
Set variable for x co position
Get the ball to detect when its hit a tile
Set y co position as a constant so it doesn’t move
Set boundary co-or for edge of screen

23. Decomposition Makes problems easier to solve
Different people can work on different parts of a problem at the same time, reducing development time
Program components developed in one program can easily be used in other programs

24. Challenges Then print the result of the calculation
1) Write a python program that inputs 2 numbers and a + - * /
Then print the result of the calculation
2) Write a Python program to input 4 numbers then calculate and print the average
3) Write a Python program to input a list of n numbers and print the average (while loop)

25. Linear search
A linear search involves methodically searching one location after another until the searched for value is found.
Data is held in consecutive locations
Data is not ordered
Good if… data cannot be ordered
Step through until...
Value found – return location
Value not found – return not found
Adam
Debbie
Chris
Felix
Aaron
John
Sarah
Will

26. Binary search In order For the binary search to work the list must be?
A binary Search is an example of a Divide and Conquer Algorithm.
“This is where you repeatedly break down a problem into smaller problems and tackle these smaller problems to build an answer to the original”
In order
For the binary search to work the list must be?

27. 2 33 1 2 3 4 5 6 7 8 2 33 1 2 3 4 5 6 7 8

28. Bubble Sort 2 1 3 6 5 4 Set swapMade = true WHILE swapMade is true
Set swapMade to false
Start at position 0
For position = 0 to listlength-2
Compare the item at position you are at with the one ahead of it
If they are out of order THEN
Swap items and set swapMade to true
END IF
Next position
End WHILE 2 1 3 6 5 4

29. Bubble Sort 2 1 3 6 5 4 Set swapMade = true WHILE swapMade is true
Set swapMade to false
Start at position 0
For position = 0 to listlength-2
Compare the item at position you are at with the one ahead of it
If they are out of order THEN
Swap items and set swapMade to true
END IF
Next position
End WHILE 2 1 3 6 5 4

30. Bubble Sort 2 1 3 6 5 4 1 2 3 6 5 4 1 2 3 6 5 4 1 2 3 6 5 4 1 2 3 6 5 4

31. Bubble Sort 1 2 3 5 6 4 1 2 3 5 6 4 1 2 3 5 4 6 1 2 3 5 4 6 1 2 3 5 4 6 1 2 3 5 4 6

32. Bubble Sort 1 2 3 5 4 6 1 2 3 4 5 6
How do we know it has finished?

33. Bubble Sort 1 2 3 4 5 6 1 2 3 4 5 6
We go through the list again and if no swaps are made then it is sorted 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6

34. Insertion Sort
Make the first item the sorted list and the remaining items are the unsorted list.
WHILE there are items in the unsorted list
Take the first item of the unsorted list.
WHILE there is an item to the left of it which is smaller than itself
Swap with that item.
END WHILE
The sorted list is now one item bigger 3 1 2 5 6 4 3 1 2 5 6 4 3 1 2 5 6 4
Sorted
Unsorted 1 3 2 5 6 4
Sorted
Unsorted 1 2 3 5 6 4
Sorted
Unsorted

35. Insertion Sort 1 2 3 5 6 4
Sorted
Unsorted 1 2 3 5 6 4
Unsorted
Sorted 1 2 3 5 6 4
Unsorted
Sorted 1 2 3 5 6 4
Unsorted
Sorted

36. Insertion Sort 1 2 3 5 4 6
Unsorted
Sorted 1 2 3 4 5 6
Unsorted
Sorted
How do you know it has finished ?
You have processed the last item in the Unsorted list and you have positioned it in the sorted list next to one that is smaller.

37. Arrays
An array is a list of data items of the same type that can referred to by the same variable name
NumberList=[3,5,7,9,11]
print(NumberList[0])
print(NumberList[1])
print(NumberList[2])
print(NumberList[3])
print(NumberList[4])

47. Should say identify the symbol

48. Should say identify the symbol