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The if statement

Learn how to check a condition with if and the code block.

The if statement

To run certain code when a condition is true you use the if statement. The condition is written inside parentheses and, if true, the block wrapped in braces runs: if (age >= 18) { std::cout << "Can drive"; }.

C++ does not use a then keyword; the parentheses and the brace block are enough. The condition must evaluate to a bool value, which the comparison operators produce. When the condition is false the block is skipped and the program moves to the next statement.

Comparison operators

Inside if conditions you often use comparison operators. == is equal, != is not equal, < is less than, > is greater than, <= is less than or equal, >= is greater than or equal.

Note: = is assignment and == is comparison. If you write if (count = 0) you reset count to zero and the result is false, so the block does not run. Always use double == for comparison.

Practice Age check

The age variable is set to 20. Use the condition if (age >= 18) to check whether the age is 18 or above and, if true, print "Can drive".

Starter code

main.cpp
#include <iostream>

int main() {
    int age = 20;
    // Write the age check here
    return 0;
}

Sample solution

main.cpp
#include <iostream>

int main() {
    int age = 20;
    if (age >= 18) {
        std::cout << "Can drive" << std::endl;
    }
    return 0;
}

Expected output

Can drive

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Which is a valid if statement?

main.cpp
if (... ) { ... }
  • if (age >= 18) { ... } Correct answer
  • if age >= 18 { ... }
  • if (age >= 18) then { ... }
  • if [age >= 18] { ... }

Explanation: The condition is in parentheses; no 'then' keyword.

2 Write the if condition

Question 
int age = 20;
if (____) { std::cout << "Access granted"; }
Answer 
int age = 20;
if (age >= 18) { std::cout << "Access granted"; }

Explanation: age >= 18 is true for 20.

3 Match each operator to its meaning

Term Meaning
== Equal
!= Not equal
< Less than
>= Greater or equal

All lessons in Beginner

1 C++ basics

  1. What is C++?
  2. Your first program
  3. std::cout
  4. std::cin
  5. Comments
  6. Summary - C++ basics

2 Variables

  1. Declaring variables
  2. auto
  3. const
  4. constexpr
  5. Type conversion
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. bool and char
  4. std::string
  5. sizeof
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Bitwise operators
  6. Summary - Operators

6 Strings

  1. std::string basics
  2. String concatenation
  3. String length
  4. Substring
  5. String search
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. The switch statement
  4. The ternary operator
  5. Nested conditionals
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. Range-based for
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding products
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Arrays

  1. C-style arrays
  2. Array access
  3. std::array
  4. Multidimensional arrays
  5. Arrays and loops
  6. Summary - Arrays

11 std::vector

  1. Declaring vectors
  2. push_back
  3. size and at
  4. Vector access
  5. Vector loop
  6. Summary - std::vector

12 Functions

  1. Defining functions
  2. Return values
  3. Parameters
  4. Function overloading
  5. Default parameters
  6. Summary - Functions

13 References

  1. What is a reference?
  2. Declaring references
  3. Reference parameters
  4. const references
  5. Dangling references
  6. Summary - References

14 Pointer basics

  1. What is a pointer?
  2. The & address operator
  3. Pointer dereference
  4. nullptr
  5. Pointer arithmetic
  6. Summary - Pointer basics

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Advanced string operations

  1. String streams
  2. stoi and stod
  3. to_string
  4. String comparison
  5. String modification
  6. Summary - Advanced strings

17 Structs

  1. Defining structs
  2. Using structs
  3. Struct and function
  4. Array of structs
  5. Nested structs
  6. Summary - Structs

18 Exception basics

  1. try/catch
  2. throw
  3. std::exception
  4. Custom exceptions
  5. catch all
  6. Summary - Exceptions

19 Namespaces

  1. Defining namespaces
  2. using
  3. std namespace
  4. Nested namespaces
  5. Namespace alias
  6. Summary - Namespaces

20 Beginner final

  1. Project design
  2. Data model
  3. Business logic
  4. Error handling
  5. Putting it together