Mastering C++ Comments: Types, Use Cases, and Practical Examples

In C++ language, comments are essential for writing clear and maintainable source code.Comments provide explanations and context, making it easier for other developers and yourself to understand the source code later without any problem. In this article, we will explore the different types of comments in C++ language and their use cases with practical examples.

What are Comments?

In C++ language, comments are used to make the code more readable and more understandable for developers  Comments are ignored by the C++ compiler, meaning they do not affect the execution of the C++ program.

The following program demonstrates the Comments:

Program

Output

Comments play a very important role in C++ programming language for various reasons, enhancing both the development process and the understandability of source code. Here, we are discussing some important points for comments in C++ language.

• Code Explanation: Comments provide explanations about what the code does, making it easier for others (or yourself) to understand the source code. This is very useful in complex programs or non-intuitive sections of source code.

• Documentation: Comments can be used to document the purpose of a function, the parameters it takes, the expected return values, and any other relevant information. This helps in maintaining and updating the source code.

• Debugging: Comment can help in debugging programs. It allows you to temporarily disable parts of the code without deleting them. It makes it easier to isolate issues and test different parts of source code .

• Clarification of Complex Logic: Comments are very helpful to clarify the complex source code which is useful for future developers or for revisiting the source code after a period of time.

• To-Do and Future Work: Comments can also be used to leave notes for future work or enhancement in source code. Sometimes developers are labeled as ‘TODO ‘ or ‘FIXME’, acting as a reminder for pending tasks or areas that require attention.

Types of Comments in C++

In C++ language, There are two types of comments used to annotate the source code. Single line comment and multi-line comments. Each type of comment serves a unique purpose and is used in different contexts in C++ language.

Single Line Comment

The single line comments are used for brief notes or explanations that fit on one line. It starts with ‘//’. Everything  after ‘//’ on that line is treated as a comment. So Anything following // on the same line will be ignored by the C++ compiler.

The following program demonstrates a single line comment:

Program

Output

Multi-Line Comments

The multi-line comments are block comments. It allows you to comment out  the multiple lines of  source code. The multiline comments starts with /* and end with */.  They can span multiple lines and are useful for longer explanations or temporarily disabling source code.

The following program demonstrates the multi-line comments:

Program

Output

How the Compiler Process Comments in C++ Language

In C++ language, Comments are ignored by the compiler during the compilation process. They are meant for human readers and are used to explain or annotate the source code without affecting its execution. The compiler processes comments as follows:

• Detection and Removal: The C++ compiler identifies the comment based on their syntax and removes them from the code before compilation. This is a very crucial step to ensure that comments do not interfere with the source code execution.

• Ignoring Comments: The compiler encounters comments in the source code. Compiler ignores the comments. Compilers do not take up any memory space in the final executable file, and they have no impact on the performance of the program.

• Preprocessing: During the preprocessing phase, the compiler removes comments along with other preprocessing directives like ‘#include’ and ‘#define’ . After this phase, the remaining source code is what will be compiled.

• Impact on Source Execution: We know that comments are not part of the executable source code, they have no impact on the program’s behavior or performance. They are purely for documentation purposes.

C-style Comments

The C-style comments originated from the C programming language. These comments are utilized to annotate multiple lines of text in the source code. The following detailed look in C-style comments.

Syntax

C-style comments starts with ‘/*’ and end with ‘*/’. Everything between these delimiters  is treated as a comment in the programming language.

Single Line Usage 

C-style line comments are designed for multi-line comments. But we can also use them for single line comments.

/* This is a single line C-style comment */

No Nesting

C-style comments cannot be nested. If developers try to nest them then it will return a compilation error.

Incorrect Usage

/*

/* This will cause an error */

*/

C++ style Comments

C++ language introduces its own comments, which provide a concise way to annotate  single lines of code.

Single Line Comments

C++ language single line comment starts with //. The following two slashes on the same line are treated as a comment.

// This is a single-line comment in C++ language

int a=5

Advantages of Single-Line Comments

Single-line comments in C++ offer several advantages, making them a valuable tool for developers.

• Clarity and Readability: Single-line comments can be used to explain specific lines or small blocks of code. Single comments making the code easier to understand.

• Inline Documentation: Single line comment allows for inline documentation, where explanations are provided directly next to the code they describe.

• Ease of Use: Adding single-line comments is quick and straightforward, often requiring less effort than multi-line comments.

• Code Debugging: Single line comments are very useful for temporarily disabling specific lines of code during debugging without affecting the surrounding source code.

Inline Comments

We can also use comments at the end of a line of source code:

This form is very common in C++ programs.

/* and */ Comments

This /* … */ is a multiline comment. It originates from the C programming language and is often referred to as C-style or block comments. These comments are used to annotate multiple lines of text or source code in the C++ programming language code .

Multi-Line Comments

C-style comments start with /* and end with */. Everything between these delimiters is treated as a comment, regardless of how many lines it spans.

Conclusion

In this article, we learned that the comments in C++ are indispensable tools for improving code readability, maintainability, and collaboration among developers. There are two types of comments in C++ language; single -line (‘//’) and multi-line (‘/*…*/’).  Comments providing insights and explanations directly within the code, comments ensure that the purpose and functionality of various code segments are clear not only to the original author but also to anyone else who may work on the project in the structure.