The role of static in c language

The static keyword is used in C language to limit the scope and life cycle of variables. Limit the scope of file local variables so that they can only be accessed within this file. Limit the scope of function local variables so that they can only be accessed within this function. Makes file scope variables exist while the program is running. Causes function scope variables to be created every time you enter the function and destroyed when you leave, but retain their value every time you enter.

The role of static in C language

Role:
static key Words are used in C language to limit the scope and life cycle of variables.

Variable scope:

• File local variables: Variables in the file declared using static can only be accessed in this file.
• Function local variables: Variables within a function declared using static can only be accessed within this function.

Variable life cycle:

• File scope: Variables in files declared using static will remain during the running of the program. exist.
• Function scope: Variables within a function declared using static are created when entering the function and destroyed when leaving the function, but their values ​​will be retained each time they enter the function.

Usage scenarios:

• Limit variable visibility: Prevent other files or functions from accidentally accessing variables.
• Implementing a singleton: Ensure that a variable has only one instance in the entire program.
• Preserve variable values: Enable variables within a function to retain their values ​​each time the function is called.
• Save data: Continue to retain some necessary data after the program exits.

Example:

File local variables:

static int globalVariable; // 只能在本文件中访问

Function local variables:

static int functionVariable; // 只能在本函数中访问，每次调用函数时保持值

Note:

• Don't use static for global variables, otherwise it may cause unpredictable side effects.
• The initialization value of a static variable must be a constant expression or 0.

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