There are two ways to put comments in C++ code:

Single-Line Comments

// starts a single-line comment which ends at newline:

int main()
{
   // This is a single-line comment
   int a;  // this also is a single-line comment
   int i;  // this is another single-line comment
}

Block Comments

Block comments can span multiple lines. They start with /* and end with */.

int main()
{
   /*
      This is a block comment.
    */
   int a;
}

Block comments can also start and end within a single line. For example:

void SomeFunction(/* argument 1 */ int a, /* argument 2 */ int b);

Importance of Comments

As with all programming languages, comments provide several benefits:

• Explicit documentation of code to make it easier to read/maintain
• Explanation of the purpose and functionality of code
• Details on the history or reasoning behind the code
• Placement of copyright/licenses, project notes, special thanks, contributor credits, etc. directly in the source code.

However, comments also have their downsides:

• They must be maintained to reflect any changes in the code
• Excessive comments tend to make the code less readable

The need for comments can be reduced by writing clear, self-documenting code. A simple example is the use of explanatory names for variables, functions, and types. Factoring out logically related tasks into discrete functions goes hand-in-hand with this.

Comment markers used to disable code