Representing algorithms for GCSE Computer Science
There are several ways to represent algorithms for GCSE Computer Science:
- Structured English
- Program statements in a particular language
In this article we are looking at flowcharts for GCSE Computer Science.
For our example, we will create an algorithm which determines whether a given whole number is even or odd. The algorithm makes use of the
MOD operator, which is represented in Python using the
% sign. The principle is simple, but it can take some practice to get used to.
MOD gives the remainder when dividing one integer by another. So for example:
- 5 divided by 2 gives 2 remainder 1
- 6 divided by 2 gives 3 remainder 0
Try running the Python code below to see how this pattern works when dividing by 2 and keeping the remainder.
for i in range(11): print(i % 2) Output: 0 1 0 1 0 1 0 1 0 1 0
Modulo operator lesson
If you want to master the modulo operator, check out this complete lesson with worksheets and practice examples, including Python code solutions.
Flowchart the Even/Odd Algorithm
The flowchart for this algorithms is shown below. Make sure you can follow it, understanding all the symbols used. There is a key for the symbols at the top of this article.
You should copy this flowchart on paper now to help remember and understand it. I recommend practicing flowcharts with paper and pencil as well as using an online tool such as draw.io
Programming the Even/Odd Algorithm in Python
Have a go now at writing the Python code for this algorithm. The solution is available by clicking on “show solution” but have a good attempt for yourself first.
# Even or odd? num = int(input("Enter a whole number: ")) if num % 2 == 0: print(num, "is even") else: print(num, "is odd.")
Flowchart practice exercise
Draw a flowchart for an algorithm which takes the base length of a square as input and prints the area of the square.
Good luck with mastering flowcharts for GCSE Computer Science.