Identifying Inputs, Processes, and Outputs

This lesson covers how to identify inputs, processes, and outputs when solving problems, as required by OCR J277 Section 2.1. This is a fundamental skill in computational thinking that helps you understand what a system needs to do before you start designing it.

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The Input-Process-Output (IPO) Model

Every computer system and algorithm can be described using the Input-Process-Output (IPO) model:

Stage	Description	Example (Calculator)
Input	Data that enters the system	The numbers to be calculated and the operation (+, -, x, /)
Process	What the system does with the input	Performs the arithmetic calculation
Output	The result produced by the system	The answer is displayed on screen

This simple model applies to every algorithm and system, from a basic calculator to a complex weather forecasting system.

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Identifying Inputs

Inputs are the data that a system receives from the user or another source. When analysing a problem, ask: "What data does the system need to work with?"

Types of Input

Input Type	Description	Example
User input	Data entered by a person	Typing a search query, entering a password
Sensor input	Data from electronic sensors	Temperature reading, motion detection
File input	Data read from a stored file	Loading a saved game, reading a CSV file
Network input	Data received from another device	Receiving an email, streaming video
System input	Data from the computer's own systems	Current date and time, mouse position

Example: Online Shopping Checkout

Input	Source
Items in basket	User selection (during browsing)
Delivery address	User input (form)
Payment details	User input (form)
Discount code	User input (optional)
Current date	System (for delivery estimate)
Stock levels	Database

OCR Exam Tip: When identifying inputs, include ALL data the system needs — not just what the user types. Remember to consider data from files, databases, sensors, and the system itself. Each input should be specific (e.g. "the user's postcode" not just "information").

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Identifying Processes

Processes are the operations performed on the inputs to produce the outputs. When analysing a problem, ask: "What does the system need to do with the data?"

Types of Process

Process Type	Description	Example
Calculation	Mathematical operations	Calculating total price, averaging scores
Comparison	Checking if values meet conditions	Is the password correct? Is the student over 16?
Sorting	Arranging data in order	Sorting search results by relevance
Searching	Finding specific data	Looking up a customer record by ID
Validation	Checking that input is reasonable	Is the age between 0 and 150? Is the email format valid?
Storage	Saving data for later use	Writing a record to a database
Transformation	Converting data from one form to another	Converting temperature from Celsius to Fahrenheit

Example: Online Shopping Checkout