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How do inputs, processes, and outputs work?

Here, we consider each of the steps that a digital device needs to perform its tasks and how you can teach these to young learners.

All digital devices receive inputs, perform processes, and deliver outputs. Here, we consider each of the steps that a digital device needs to perform its tasks and how you can teach these to young learners.


All digital devices accept inputs. An input is data that is entered in to or received by a computer. This could include a user pressing a key on a keyboard, clicking a mouse to select something on screen, or a light sensor sensing light levels. Some inputs indicate to the digital device what we want it to do, while others provide data for the device to process.

Inputs don’t always have to be initiated by human beings. For example, a temperature sensor could gather and input data into a device or a message could be received by one device from another device.


The process determines what the device does with the input. The same input can be processed in different ways. For example, in word processing software, when you press the letter A on a keyboard, the computer may process the input and display it as a letter A on the screen. When using a Crumble, the process might use a button as input to determine what colour a Sparkle will need to be set to.

Crumble code - 'Program start' and 'set sparkle 0 to red'.

The programme contains the set of instructions that define the process. In the programme above, the user will start the programme by clicking on the green play arrow in the Crumble software. This will trigger the process which is shown in the code; the Crumble will send a signal to the Sparkle to tell it to light up red.


The output is how the digital device presents the results of the process. Outputs can be returned to the user in many ways, such as text on a screen, printed materials, or sound from a speaker. On a Crumble, outputs could include a motor turning or, as in the program above, a Sparkle lighting a certain colour.

Helping learners to understand input, process, and output

Younger learners do not need to know how the digital device actually processes the data, but should be aware that something has happened between the input being entered into the device and the output being produced. You can model this with an ‘input-process-output machine’, like the one shown in the diagram below.

An animation of an IPO machine. A small football goes into the machine through an input funnel. A screen reads 'Process: Make it bigger!'. A large football then comes out of the output funnel.

In this example, the input in to the machine is a football. The machine then gives an output (on the right). In this case, the process that the machine has carried out is to make the football bigger or scaled up. Introducing younger learners to simple examples of input, process, output, using models like this, can help you to develop their understanding of the input-process-output model at a basic level. They can then apply this model to digital devices, starting with familiar ones, like a digital camera.

Illustration of a digital camera.

  • Input – The user presses the button on the top
  • Process – The camera captures and stores a picture
  • Output – The image is shown on the screen

An understanding of how inputs, processes, and outputs (IPO) work in real world digital devices will be useful for your learners when creating their own physical computing projects. Being aware that an input will trigger a specific process and produce the desired output will help learners to choose appropriate components for their projects.

Below, I’ve shown how lights (Sparkles) and motors can be connected to a Crumble controller, and then split into input, process, and output.


  • Input – The user clicks on the green arrow to start the programme
  • Process – The Crumble checks for input, and when it is received, sends a signal to change the colour of the Sparkle

    Crumble code - 'Program start' and 'set sparkle 0 to red'.

  • Output – The Sparkle lights up in the specified colour


  • Input – The user clicks on the green arrow to start the programme
  • Process – The Crumble checks for input, and when it is received, sends a signal to turn the motor

    Crumble code - 'Program start' and 'motor 1 forward at 75%'.

  • Output – The motor turns

IPO in lessons

The concept of input, process, output is fundamental to computing — no matter how big or complicated the system is. By using relatable examples and connecting them to the concept, you can help your learners develop a firm understanding of IPO, that they can then apply both in their physical computing projects, and more widely.

Much of the above content is part of the Year 3 (aged 7–8 years old) – Computing systems and networks – Connecting computers unit of the Teach Computing Curriculum. This unit includes a range of activities to help you to teach learners about digital devices and the concept of IPO.

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Teaching Physical Computing to 5- to 11-year-olds

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FutureLearn - Learning For Life

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