Summary of C language about notes

When writing C source code, you should use annotations to help you understand the code. There are two ways to annotate in C:

1.1 Block comments that start with /* and end with */ (block comment);

2. The other is a single-line comment that starts with // and ends with a newline (line comment).

You can use the /* and */ delimiters to annotate comments within a line or multiple lines of comments. For example, in the following function prototype, the ellipsis means that the open() function has a third argument, which is optional. The comment explains the use of this optional parameter:

int open( const char *name, int mode,  ...  /* int permissions */ );

You can use // to insert an entire line of comments, or write the source code in two columns, with the program in the left column and the comments in the right column:

const double pi = 3.1415926536;    // pi Is a constant 

In the C99 standard, single-line annotations were officially added to the C language, but most compilers supported this usage before C99. Sometimes referred to as the "C++ style" annotation, it is actually derived from BCPL, the predecessor of C.

In quotes, if you use /* or // to separate 1 character constant or string literal (string literal), they are not considered the beginning of the comment. For example, the following statement is not commented:

printf("Comments in C begin with /* or //.\n" );

The preprocessor detects characters in a comment only by checking the end of the comment, so block comments cannot be nested. However, you can use /* and */ annotations to contain single-line annotations of the source code:

/*  Comment out these two lines temporarily: 

  const double pi = 3.1415926536; // pi is 1 A constant 

  area = pi * r * r;  //  Calculating area 

 Comment this for the time being  */

If you want to comment out parts of a program that contain block comments, you can use the conditional preprocessing command:

#if 0

 const double pi = 3.1415926536;  /* pi is 1 A constant    */

 area = pi * r * r ; /*  Calculating area    */

#endif

The preprocessor replaces each comment with a space. Therefore, min/*max*/Value becomes two tags min Value.

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