Detailed explanation of C language comments

When writing C language source code, you should use more comments to help understand the code. There are two comment methods in C language:

1. One is a block comment starting with /* and ending with */;

2. The other is A single-line comment starting with // and ending with a newline character.

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

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

You can use // to insert a whole line of comments, or write the source code in a two-column format, with the program in the left column and the comments in the right column:

const double pi = 3.1415926536; // pi是—个常量

In the C99 standard, single-line comments were officially added to the C language, but most compilers had begun to support this usage before C99. Sometimes they are called "C-style" comments, but in fact they are derived from BCPL, the predecessor of C.

In quotation marks, if /* or // are used to separate a character constant or string literal, they will not be considered the beginning of a comment. For example, the following statement has no comments:

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

The preprocessor only detects characters in comments by checking the end of the comment, so block comments cannot be nested. However, source code containing single-line comments can be commented using /* and */:

/* 暂时注释掉这两行： const double pi = 3.1415926536; // pi是一个常量 area = pi * r * r; // 计算面积 暂时注释到此 */

If you want to comment out part of the program containing block comments, you can use the conditional preprocessing command:

#if 0 const double pi = 3.1415926536; /* pi是一个常量 */ area = pi * r * r ; /* 计算面积 */ #endif

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

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