Thinking Ahead

Thinking ahead means identifying what is needed before you start solving a problem — the inputs, outputs, pre-conditions, and post-conditions. It also involves considering caching and reusable components to make solutions more efficient. This is a key part of OCR H446 section 2.1.

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Inputs and Outputs

Before writing any code or designing any algorithm, you must clearly identify:

Concept	Definition	Example (sorting problem)
Inputs	The data the system receives	An unsorted list of integers
Outputs	The data the system produces	A sorted list of integers
Processing	The transformation applied to inputs to produce outputs	A sorting algorithm (e.g., merge sort)

Why identify inputs and outputs first?

• It defines the scope of the problem — what exactly are you solving?
• It clarifies what data you need to collect or receive
• It determines what the user expects to see
• It helps you design test cases (you know what should go in and what should come out)

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Pre-conditions