Sequence, selection and iteration

Overview

The three programming constructs, count-controlled and condition-controlled loops, the output of for, while and do … until loops, if … elseif, and switch … case.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Name the three basic programming constructs that control the flow of a program.

   Model answer

   The three constructs are sequence, selection and iteration. Every program can be built from these three.

2. 2

   What is sequence in a program?

   Model answer

   Sequence means instructions are carried out one after another in the order they are written. Changing the order can change the result.

3. 3

   What is selection?

   Model answer

   Selection uses a condition to decide which block of code runs. The if statement and the switch statement both perform selection.

4. 4

   What is iteration?

   Model answer

   Iteration repeats a block of code. The repetition continues a set number of times or until a condition is met.

5. 5

   What is the difference between a count-controlled loop and a condition-controlled loop?

   Model answer

   A count-controlled loop repeats a fixed number of times, like a for loop. A condition-controlled loop repeats until a condition changes, like a while loop.

6. 6

   How many times is Hi printed by for i = 3 to 7, print("Hi"), next i?

   Model answer

   The word Hi is printed 5 times. The variable i takes the values 3, 4, 5, 6 and 7, and both ends are included.

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The same content, four other ways.

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