What is the role of static keyword in c++?

The functions are: 1. Modify the local variables of the function; 2. Modify the global functions and global variables; 3. Modify the member variables in the class; 4. Modify the member functions of the class.

static function:

1. Local variables that modify functions:

Features: There is a default value of 0, it is only executed once, the memory is opened at the beginning of the operation, and the memory is placed globally

2. Modify global functions and global variables:

Features: Can only be used in the original source file

3. Modify member variables in the class:

Features: Similar to 1, define multiple static y, But there is only one y, which does not enter the size calculation of the class and does not depend on the existence of the class object (can be called directly, and an external declaration is required)

4. Modify the member function of the class:

Features: f(): There is no this pointer in the brackets. You can only call its static functions of this class and its static variables, which are modified with static and do not depend on the existence of the class object. Exists (can be called directly without external declaration)

Extended information:

Main usage of static:

1. Static method

static method is generally called a static method. Since static methods can be accessed without relying on any object, there is no this for static methods. , because it is not attached to any object. Since there is no object, there is no such thing as this. And due to this feature, non-static member variables and non-static member methods of the class cannot be accessed in static methods, because non-static member methods/variables must rely on specific objects before they can be called.

But it should be noted that although non-static member methods and non-static member variables cannot be accessed in static methods, static member methods/variables can be accessed in non-static member methods.

2. Static variables

static variables are also called static variables. The difference between static variables and non-static variables is: static variables are shared by all objects and have only one copy in the memory. It is initialized if and only when the class is first loaded.

Non-static variables are owned by the object and are initialized when the object is created. There are multiple copies, and the copies owned by each object do not affect each other. The initialization order of static member variables is initialized in the order in which they are defined.

3. Static code block

The static keyword also plays a key role in forming a static code block to optimize program performance. A static block can be placed anywhere in a class, and there can be multiple static blocks in a class.

When the class is loaded for the first time, each static block will be executed in the order of the static blocks, and will only be executed once. Why the static block can be used to optimize program performance is because of its characteristics: it will only be executed once when the class is loaded.

Recommended tutorial: "C Language Tutorial"

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