Comments
Part of the Fundamentals section of Coddy's C++ journey — lesson 3 of 74.
Comments are notes you write inside your code. The compiler completely ignores them - they exist only to help humans understand the code.
To write a single-line comment, use //. Everything after // until the end of the line is ignored:
// This is a comment
std::cout << "Hello, World!";A comment can also be written at the end of a line, after the code:
std::cout << "Hello, World!"; // This prints Hello, World!For comments that span several lines, use /* to start and */ to end:
/* This is a multi-line comment.
The compiler ignores all of it. */
std::cout << "Welcome!";Comments can also temporarily disable a line of code without deleting it. This is called commenting out:
// std::cout << "This line will NOT run";
std::cout << "This line will run";
Challenge
BeginnerFix the code so that only Hello, C++! is printed.
- Replace the
?with the symbols that turn a line into a comment - The line printing
Goodbye!should become a comment so it does NOT run - Only change the line that starts with
?
Cheat sheet
Comments in C++:
- Notes for humans - the compiler ignores them
- Can disable code temporarily without deleting it
Single-line comment:
// This is a comment
std::cout << "Hello!"; // Comment after codeMulti-line comment:
/* This is a
multi-line comment */Disabling code:
// std::cout << "This will NOT run";
std::cout << "This will run";Try it yourself
#include <iostream>
int main() {
// Type your code below
? std::cout << "Goodbye!" << std::endl;
std::cout << "Hello, C++!" << std::endl;
return 0;
}
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Fundamentals
4Operators Part 1
Arithmetic OperatorsModulo OperatorIncrement/DecrementPost Increment/DecrementArithmetic ShortcutsComparison OperatorsString Comparison
3Variables Part 2
Type DeclarationNaming ConventionsRecap - Initialize VariablesType Casting Part 1Type Casting Part 26Decision Making
If StatementIf - ElseSwitch StatementConditional OperatorRecap - If ElseNested If - Else