c语言不同范围变量运算
    English Answer.
    Introduction.
    In C programming, variables can have different scopes, which determine their visibility and lifetime within a program. The two main types of scopes are local scope and global scope. Local variables are declared within a function or block and are only accessible within that scope. Global variables, on the other hand, are declared outside of any function or block and are accessible from anywhere in the program.
c语言暑期培训班
    Local Variables.
    Local variables are declared using the `auto` storage class specifier or by default if no storage class specifier is provided. They are created when the function or block in which they are declared is entered and are destroyed when the function or block exits. Local variables can be accessed using their names within the scope in which they are declared.
    Global Variables.
    Global variables are declared outside of any function or block and are accessible from anywhere in the program. They are created when the program starts and are destroyed when the program exits. Global variables can be accessed using their names from any function or block.
    Variable Lifetime.
    The lifetime of a variable refers to the period during which it exists in memory. Local variables have a limited lifetime and only exist within the scope in which they are declared. Global variables have a global lifetime and exist for the entire duration of the program.
    Variable Visibility.
    The visibility of a variable refers to the parts of the program from which it can be accessed. Local variables are only visible within the scope in which they are declared. Global variables are visible from anywhere in the program.
    Example.
    The following code demonstrates the different scopes of variables in C:
    c.
    #include <stdio.h>。
    int global_variable; // Global variable.
    void function() {。
      int local_variable; // Local variable.
      printf("Global variable: %d\n", global_variable);
      printf("Local variable: %d\n", local_variable);
    }。
    int main() {。
      global_variable = 10;
      function();
      return 0;
    }。
    Output.
    Global variable: 10。
    Local variable: 0。
    In the above code, the `global_variable` is accessible from both the `main` function and the `function`. The `local_variable` is only accessible within the `function`.
    Mixing Local and Global Variables.
    It is generally not considered good practice to mix local and global variables in a progra
m. Global variables can lead to namespace pollution and make it difficult to track variable usage. It is recommended to use local variables whenever possible and to limit the use of global variables to situations where they are truly necessary.

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