What does the shady name in c language mean?

In C, the pound sign (#) is used for the following purposes: Preprocessing directives (e.g. #include) macro definitions (e.g. #define PI 3.14159) line comments (e.g. // This is a line comment) escape characters (e.g. char c = '\#';) specify character set (e.g. "This is a string in the ASCII character set.\#";)

The meaning of pound sign (#) in C language

In C, the pound sign (#) symbol is used for the following purposes:

1. Preprocessing instructions

The most common use of the pound sign is to start with a preprocessing instruction. The preprocessing directive begins with a pound sign, followed by the instruction name, and is used to operate on the compiler before it compiles the source code into executable code. For example:

 <code class="c">#include <stdio.h></stdio.h></code>

This preprocessing directive instructs the compiler to include a header file named <stdio.h></stdio.h> before compiling the source code.

2. Macro definition

The pound sign is also used to define macros. Macros are symbols that will be replaced by specific values. For example:

 <code class="c">#define PI 3.14159</code>

This macro definition defines the symbol PI as the value 3.14159 .

3. Line comments

The pound sign can also be used to create line comments. Line comments start with a pound sign and continue until the end of the line. For example:

 <code class="c">// 这是一个行注释</code>

This line of code will not be compiled and is only used to provide information to programmers.

4. Escape characters

In character literals, the pound sign is used as an escape character. It identifies the next character as a non-standard character. For example:

 <code class="c">char c = '\#';</code>

This line of code assigns the character # to the variable c .

5. Character Set

In string literals, the pound sign can be used to specify the character set. For example:

 <code class="c">char str[] = "This is a string in the ASCII character set.\#";</code>

This line of code defines a string where the # symbol indicates the beginning of the line comment.

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