Trace tables
A trace table records every variable at each step, to check the algorithm works.
| Pass | n | n > biggest? | biggest after |
|---|---|---|---|
| 1 | 7 | No | 7 |
| 2 | 3 | No | 7 |
| 3 | 12 | Yes | 12 |
| 4 | 5 | No | 12 |
e.g.Example
Output: 12. Correct.
Iteration: count-controlled and condition-controlled loops
PracticalPresent ▶
What this lesson covers
Topic 11 Algorithms
KS3 Computing · An algorithm is a precise, step-by-step plan to solve a problem. Computational thinking turns a messy problem into one. Every algorithm is built from just three things: sequence, selection and iteration.
ProgrammingCambridge Lower Secondary Computing 0860
You will learn to
- Explain the difference between a count-controlled loop and a condition-controlled loop.
- Use repeat to draw a shape with fewer blocks.
- Use repeat until to keep going until something happens.
- Trace a loop and count how many times it runs.
Success criteria
- I can draw a square with repeat 4 instead of eight separate blocks.
- I can make a sprite keep moving until it touches something.
- I can say how many times a loop will run before I run it.
Key words
Say each word, then read what it means. Every one is in the glossary too.
- trace table
- Records variable values step by step to check logic.
- Algorithm
- Precise, ordered, finite steps to solve a problem.
- Decomposition
- Breaking a problem into smaller ones.
- Abstraction
- Ignoring detail that doesn't matter for the problem.
- Sequence · selection · iteration
- Steps one after another. First this, then this.
- Pseudocode
- Code-like writing for algorithms, without strict rules.
- Variable
- A named place in memory that holds a value.
The explanation
Read it here, or open the study page below to go one step at a time with things to try.
Study it
Open the study page and go one step at a time.
The steps for this lesson
- Topic 11, step 9: Trace tables (Trace 'find the biggest')
Try it
Check yourself
One question at a time. The reason shows after each answer.
Saved on this device.