What does _ in c++ mean?

The "_" symbol in C is used to: 1. Handle function parameters that conflict with keywords; 2. Mark unused variables; 3. Namespace qualification; 4. Macro preprocessor; 5. Anonymous union or enumeration member.

The "_" symbol in C

The "_" symbol in C is also called the underscore, It has the following uses:

1. Function parameters

• When function parameter names conflict with keywords or other identifiers, underscores can be used as replacements .
• For example, if you want to create a function named "int", you can name it "_int".

2. Unused variables

• If the variable does not need to be used, you can add an underscore before the variable name.
• The compiler ignores variables with underscores, helping to avoid compiler warnings.
• For example, create an unused variable "i": _i = 0;

3. Namespace qualification

• In namespace qualification, the underscore indicates the current namespace.
• Members of other namespaces can be accessed within the current namespace by preceding them with two underscores.
• For example: using namespace std; cout << _ _ a;

4. Macro preprocessor

• Underscores can be used in macro preprocessors to expand macros or represent macro parameters.
• For example: #define MACRO(x) _x_

##5. Anonymous union or enumeration

In unions and enumerations, underscores can represent anonymous members.
• Anonymous members do not allocate names or memory space.
• For example:
• union { _; int i; };

Note: Although the underscore has a specific purpose in C, But you can still use it to name identifiers. However, it's best to avoid using names that conflict with the compiler's built-in purposes.

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