C++ · Beginner level

Beginner level · Module 2: Control Flow and Functions in C++ · Lesson 1 of 3

Decisions and Loops

Control what runs with if/else and switch, and repeat work with for, while and do-while loops.

In this lesson you will

  • Write conditions with comparison and logical operators
  • Choose the right loop for counted and conditional repetition

Key concepts

if / else if / elseswitchfor and whileinfinite loop

The lesson

Conditions are bool expressions: score >= 50, age < 18 && hasConsent. if / else if / else runs the first true branch. switch compares one integer or character against fixed cases; remember break at the end of each case, or execution falls through to the next.

A for loop suits counted repetition: for (int i = 0; i < 10; ++i). A while loop repeats while a condition holds, such as reading values until the user enters 0. A do-while loop runs at least once, which suits menus.

When reading numbers in a loop, check that the read succeeded: while (std::cin >> value) stops cleanly at the end of input or when non-numeric text is typed.

Step by step

  1. Write a grade classifier with if / else if.
  2. Rewrite a menu choice with switch, including break statements.
  3. Read numbers until 0 and print their sum and count.
  4. Make a do-while menu that repeats until Exit is chosen.

Practice activity

Write a till loop that reads prices until 0 and prints the item count, total and average.

Expected result: Prices 2000, 3500 and 1500 followed by 0 give 3 items, total 7000 and average 2333.33.

Check your understanding

  1. What happens if a switch case has no break?

    Show answer

    Execution falls through into the next case.

  2. Which loop always runs at least once?

    Show answer

    do-while.

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