Validation, Running Totals and Array Traversal
Describe, design and implement input validation, running totals inside loops and complete traversal of one-dimensional arrays.
How to study National 5 Computing Science
Move from functional requirements to designs and implementation, trace data and code carefully, and support testing and evaluation with evidence.
Core concepts
Concept 1
Input validation repeatedly rejects data that does not satisfy the permitted condition.
Exam cue: Invert the valid condition carefully when constructing a validation loop.
Concept 2
A running total is initialised before a loop and updated during each relevant iteration.
Exam cue: Set the accumulator before the loop and use correct bounds for every array position.
Concept 3
Array traversal visits each required index exactly once unless the problem states otherwise.
Risk pitfalls and guardrails
Displaying an error without asking for replacement input inside the validation loop.
Guardrail: Check option route, data type, valid boundary, loop condition, array index, identifier and expected output before committing to the response.
Resetting a running total during each iteration.
Guardrail: Check option route, data type, valid boundary, loop condition, array index, identifier and expected output before committing to the response.
Missing the first or last array element.
Guardrail: Check option route, data type, valid boundary, loop condition, array index, identifier and expected output before committing to the response.
Memory anchors
Input validation
Repeat input until the value satisfies the allowed condition.
Validation message
Explain invalid input and request a new value inside the loop.
Running-total start
Initialise the accumulator before repetition begins.
Running-total update
Add the current relevant value during each loop iteration.
Array traversal
Visit every required index in the one-dimensional array.
Bounds check
Confirm the first index, final index and loop endpoint before tracing.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What is a trace of selection intended to record?
If points = 10, which statement changes it to 30?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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