for and while repeat code; careful termination conditions avoid infinite loops.
Loops repeat code: for iterates over a range or collection, while repeats until a condition fails. break exits, continue skips an iteration. Ensure the condition eventually becomes false; off-by-one errors are common. Complexity grows with nested loops.
Summing 1 to 100 with a for loop gives 5050.
Loops repeat work over data or until a condition is met, which is how programs process lists, streams and time-based tasks.
for and while repeat code; careful termination conditions avoid infinite loops.
Loops repeat work over data or until a condition is met, which is how programs process lists, streams and time-based tasks.
Use for when you know the number of iterations or are walking a collection, and use while when the stopping depends on a condition that may change.
Make sure the condition will eventually become false, update the loop variable correctly, and include a timeout or guard where input is external.
Typical applications include processing every line of a log file, polling a sensor until it reports ready and computing a running total over a series of measurements.
Study "Control flow" first (topic 5 of 104 in Software & Computing). It covers the groundwork this topic builds on.
Loop invariants. Iterators and comprehensions. Infinite loop hazards.
Summing 1 to 100 with a for loop gives 5050.
The next topic is "Functions", which builds directly on this one.
It is classed as Beginner in Software & Computing (topic 6 of 104). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.