IPO (Input-Process-Output) is one of the most fundamental design patterns. And it makes perfect sense.
Before a computer can operate on data, the data need to be entered at an input device.
Now calculations may be performed.
And, finally, a result may be displayed on an output device.
Consider some variants on this design pattern. Let's say that you are asked to enter two numbers, to add them then display the sum. For this program, you might have two enter processes at the beginning, (enter firstNumber, then enter secondNumber). The calculate operation is the addition. The display operation shows the sum on the output device.