1.2 How Systems Are Structured and Function
Represent and organise numbers, text, images and sound; compare data and file structures; and analyse automated systems.
How to study WJEC GCSE Computer Science
Learn the computing principle, apply it to the named system or scenario, trace the data and control flow, and test the result against requirements.
Core concepts
Concept 1
Denary, binary and hexadecimal conversion, binary addition, shifts, overflow, underflow, units, character sets, images, sound and compression ratios
Exam cue: Identify the current WJEC unit, the command word and whether the task asks for knowledge, application or computational analysis.
Concept 2
Primitive and compound data types, one- and two-dimensional structures, records and file organisation
Exam cue: Show place-value or storage calculations explicitly, then link the chosen representation or structure to accuracy, capacity and processing needs.
Concept 3
Inputs, processing, outputs, feedback and control in automated systems
Exam cue: Use precise terminology, trace inputs and state changes, and test the answer against the data, scenario or program behaviour.
Risk pitfalls and guardrails
Confusing a data type with a data structure, or claiming that lossy compression can always recreate the original data.
Guardrail: Avoid generic descriptions, unchecked traces and cross-board assumptions; make every answer depend on the named data, system, algorithm or scenario.
Importing the legacy WJEC structure, a different board's content or a Foundation/Higher tier assumption.
Guardrail: Use qualification code 3460QS or 3460CS and the current two-unit untiered structure; do not import a legacy or cross-board route.
Giving a generic description without applying it to the named system, data set, algorithm or pre-release scenario.
Guardrail: Practice cannot replace the annual live brief, specified Python environment, clean-copy rule, restricted examination files or Surpass upload process.
Memory anchors
Binary and hexadecimal
Binary uses base 2; hexadecimal uses base 16 and provides a compact representation of binary values.
Character encoding
A character set maps characters to numeric codes; Unicode supports a much wider range than ASCII.
Image storage
Bitmap size depends on pixel dimensions and colour depth; metadata may store additional properties.
Sound storage
Digital sound quality and size depend mainly on sample rate, bit depth and duration.
Lossless and lossy compression
Lossless compression recreates the original; lossy compression removes data to reduce size further.
Automated control
Sensors provide input, a processor applies rules and actuators produce outputs, often using feedback.
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 decimal value does binary 101101 represent?
Convert binary 11100010 to decimal.
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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