Constructs
Overview
Every program you will ever write, however large, is built from just three basic constructs repeated and combined: doing things in order, choosing between different paths, and repeating a set of instructions. Master these three and you can structure almost any solution; get them wrong and even a well-planned algorithm will misbehave.
This lesson works through sequence, selection and iteration in Python, including nesting one construct inside another, and the crucial distinction between a loop that runs a known number of times and a loop that keeps running until a condition changes. Every example uses Python, one of the three languages, alongside C# and Java, permitted for the Paper 2 practical exam.
Objectives
- Understand the structural components of a program (variable and type declarations, command sequences, selection, iteration, data structures, subprograms)
- Be able to use sequencing, selection and iteration constructs in their programs
Mind map
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Flashcards
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Constructs. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Which construct executes instructions one after another in the order they are written? A) Selection B) Iteration C) Sequence D) Subprogram Answer: C
- A loop must run exactly 20 times. Which type of iteration is most appropriate? A) Condition-controlled B) Count-controlled C) Nested selection D) Sequence Answer: B
- In Python, which keyword starts a condition-controlled loop? A) for B) while C) if D) def Answer: B
- What determines which construct a line of Python code belongs to when constructs are nested? A) The order variables are declared B) The line's indentation C) The number of comments above it D) The variable names used Answer: B
- A while loop's condition never becomes false because the loop body never updates the variable it depends on. What is the result? A) A syntax error B) The loop runs zero times C) The loop never terminates D) The loop automatically corrects itself Answer: C
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