B7.4.2.1.1 B7 (JHS 1) · Computational thinking · Algorithm
Sequence, selection, and iteration
You should be able to: explain algorithm, decomposition, and abstraction, and use sequence, selection, and iteration in a simple plan.
1. Learn
An algorithm is a clear, finite list of steps to solve a problem. Cooking jollof from a recipe is an algorithm. So is “how to pay school fees with MoMo”.
- Decomposition — break a big problem into smaller ones. “Organise a sports day” → budget, teams, first aid, timetable.
- Abstraction — hide extra detail so you can think. A trotro map shows stops, not every pothole.
Three ways steps flow:
- Sequence — one after another, no branching. Example: wake up → brush teeth → wear uniform → go to school. Numbers 1 to 10 in order are a sequence.
- Selection — a decision. If it is raining, take an umbrella; else leave it. Tea with sugar or without sugar still results in tea.
- Iteration — repeat. Keep adding pupils’ scores until the list ends. Keep stirring until the soup thickens. Lightbot-style puzzles use iteration when you repeat “move forward”.
2. See
Draw three small flow sketches: a straight line of boxes (sequence); a diamond “yes/no” (selection); an arrow looping back (iteration). If you can, try a Lightbot or Scratch “repeat” block.
3. Practice
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Write your morning from waking to reaching the school gate as a sequence of 6–8 steps. No “if” yet.
Show a sample
Wake → wash → eat → wear uniform → take bag → walk to junction → board trotro → alight at school → enter gate.
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Add selection: what changes if it is raining?
Show a sample
If raining, wear a raincoat / take a taxi if you can; else walk as usual. You still arrive at school (same outcome, different path).
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Give an everyday iteration example in a Ghanaian market.
Show a sample
The seller keeps weighing and packing tomatoes until the customer’s bowl is full, or keeps calling prices until the last customer leaves.
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Decompose “send homework by email” into at least four smaller tasks.
Show a sample
Open mail → attach file → type teacher’s address → write subject → send → check Sent folder.
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Why is a map of Accra an example of abstraction?
Show answer
It keeps useful things (roads, names) and leaves out extra detail (every house colour, every pothole) so you can plan a route.
4. Project (GES exemplar)
Write numbers 1–10 in order (sequence). Write a day’s itinerary with no branching. Then present a case with two options that still meet the same goal (selection). Then design a small solution that uses iteration (Lightbot or a loop in words).
Submit: one page with three labelled mini-algorithms: Sequence / Selection / Iteration.
5. Check (GES proficiency)
- Emerging — lists steps but they jump around
- Developing — sequence is clear; selection and iteration are mixed up
- Approaching proficient — three correct mini-examples
- Proficient — uses decomposition and abstraction in the write-up
- Highly proficient — a classmate can follow the algorithms without extra talk
Source: NaCCA Computing CCP B7.4.2.1 / B7.4.2.1.1. SURF-CLOUD Technology Institute.