An input-output pathway describes how data travels through a system: an input device captures it, the processor works on it, storage keeps what must be kept, and an output device presents the result. Explaining a pathway means naming each stage in order and saying what happens at it.
This lesson belongs to the hardware, software and systems module and joins the earlier ideas about devices, software and storage into one sequence.
What are the stages?
- Input: data enters the system through a device such as a keyboard, a scanner, a microphone or a sensor.
- Processing: the processor, running software, changes or uses the data.
- Storage: data or results are written to a storage device if they must be kept. Some pathways read stored data first.
- Output: the result is shown, printed or played through a device such as a monitor, printer or speaker.
Not every pathway uses all four stages. Say honestly which stages the scenario includes.
How do you write a pathway?
- Start with the trigger: what does the user do first?
- Name the input device and the data it captures.
- State the processing in one verb phrase: “compares the code with the price list”.
- Add storage if the scenario saves or looks up data.
- End with the output device and what appears on it.
Worked example
A shop assistant scans a barcode on a tin of beans. The till shows the name and price and prints a receipt at the end. Explain the pathway.
Input: the barcode scanner reads the number in the barcode.
Processing: the till’s processor takes that number and searches the product list for a match.
Storage: the product list is kept on a storage device. It is read, not changed, at this point. The sale itself may be written to storage as a record.
Output: the monitor shows the product name and price, and the printer prints the receipt.
Joined into one explanation: the scanner inputs the barcode number, the processor matches it to the stored product list, and the screen and printer output the price and receipt.
Notice every sentence says what the part does, not only its name.
What mistake do students make?
The usual slip is to list devices without the processing step.
Mistaken answer: “Scanner, hard disk, monitor.”
The hard disk is storage, not an output device, and nothing says what the system did with the barcode.
The correction is to write one short clause per stage, using the pattern “device, then action, then result”.
Check yourself
1. A student speaks into a microphone and the words appear on screen as typed text. Name the input device, the output device and the processing.
Show answer
Input: microphone. Processing: software converts the sound into text. Output: the monitor shows the text.
2. A weather station sensor records the temperature each hour and saves it. Which stage is the saving?
Show answer
Storage. The readings are written to a storage device so they can be used later.
3. Why is a speaker an output device and not a storage device?
Show answer
It presents data to the user as sound. It does not keep the data once the sound has played.
Where does this lead next?
Go on to analogue quantities and digital representations, which explains how a sensor reading becomes something a processor can use. The mixed practice set includes pathway questions.
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