In C++, comments are used to provide explanations or annotations in the code. They are ignored by the compiler and do not affect the program's execution. C++ supports two types of comments:

1. Single-line comments
2. Multi-line comments

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1. Single-Line Comments

A single-line comment begins with // and extends to the end of the line. Anything written after // on the same line is ignored by the compiler.

Example:

cpp
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#include 

    int main() {
        // This is a single-line comment
        std::cout << "Hello, World!" << std::endl; // Print Hello, World!
        return 0;
    }
    

• // This is a single-line comment: This comment explains that it’s a single-line comment.
• // Print Hello, World!: Describes the purpose of the std::cout statement.

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2. Multi-Line Comments

Multi-line comments start with /* and end with */. Everything between /* and */ is treated as a comment, even if it spans multiple lines.

Example:

cpp
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#include 
    
    int main() {
        /* This is a multi-line comment.
           It can span multiple lines
           and is ignored by the compiler.
        */
        std::cout << "Hello, World!" << std::endl;
        return 0;
    }
    

• /* ... */: The multi-line comment can span multiple lines and is useful for longer explanations or temporary code disabling.

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Use Cases for Comments

• Documentation: Comments explain the purpose of code segments, making it easier to understand.

  cpp
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  // This function adds two numbers and returns the result
      int add(int a, int b) {
          return a + b;
      }
      

• Code Debugging: Comments can temporarily disable code during debugging.

  cpp
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  // std::cout << "This line is temporarily disabled" << std::endl;
      

• Multi-line comments for larger explanations:

  cpp
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  /*
      This program demonstrates the use of basic input and output in C++.
      It takes a number from the user and displays it on the screen.
      */
      

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Best Practices for Comments

1. Keep comments relevant and concise: Write clear and meaningful comments.

2. Avoid redundant comments: Do not restate what the code is already doing.

   cpp
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   int x = 5; // Setting x to 5  <-- Redundant
       

3. Use comments to explain the "why" instead of the "what": Instead of explaining how the code works, describe why it's doing something.

4. Use single-line comments for short explanations and multi-line comments for detailed explanations.

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Summary

• Single-Line Comments: Use // for comments that fit on one line.
• Multi-Line Comments: Use /* ... */ for comments that span multiple lines.
• Comments are crucial for making code readable and maintainable by explaining the purpose and reasoning behind specific code blocks.