## Representing algorithms for GCSE Computer Science

There are several ways to represent algorithms for **GCSE Computer Science**:

- Structured English
- Flowchart
- Pseudocode
- 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.

### 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.**