lesson
Clean representation without changing meaning
1 · Learn
Validation checks whether input meets rules; normalisation puts equivalent representations into a consistent form. Trimming accidental surrounding spaces can help compare a menu command, but blindly deleting meaningful characters can corrupt data.
Reject invalid input clearly and preserve the user's opportunity to correct it. Validation does not prove that a plausible value is true or that an authorised person supplied it.
2 · Worked example
A score restricted to integers from 0 to 100 rejects 101. A supplied score of 90 fits the range but could still be factually wrong.
3 · Your turn
Does passing a 0–100 range check prove a test score was recorded truthfully?
Check your answer
No. It establishes only that the value meets that rule.
4 · Apply your learning
Design boundary, invalid-type and ordinary-value tests using invented scores.
Adult guidance and safety
Use an approved sandbox with invented data. Never ask for real passwords, personal records or access to another person's system. These text examples need executable projects and assessed evidence in two languages; reading code alone is not practical mastery.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
Powers, roots and trigonometry · Year 7 onward
Use only when the task allows a calculator. Choose one operation at a time and record your working. Trigonometry here always uses degrees (DEG), not radians. Inverse sine, cosine and tangent return an angle, not a reciprocal. Keep exact fractions and π in answers when requested.
Approximate numerical results use up to 12 significant digits. Inverse sine returns −90° to 90°, inverse cosine 0° to 180°, and inverse tangent −90° to 90°; these are principal values, not every possible solution of a trigonometric equation.
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