What are the characteristics of external variables in the C programming language?

Characteristics of external variables (global variables) in the C language include:

1. Long lifespan: External variables are created when the program starts running and are destroyed when the program ends, their lifespan being the same as the entire program’s execution.
2. Global visibility: External variables can be accessed and used in any part of the program without being limited by scope.
3. External variables remain in memory at all times during program execution when stored in the static storage area, regardless of whether the function in which they are located is executed.
4. By default, initialized to 0: If external variables are not explicitly initialized, C language will initialize them to 0 by default.
5. Variables can be shared by multiple functions: external variables can be shared and accessed by multiple functions in the program, allowing for data transfer and sharing between different functions.
6. Potential causes of naming conflicts arise due to the global visibility of external variables. If a program contains multiple external variables with the same name, it can lead to naming conflicts and chaotic code.
7. You can declare with the keyword extern: If you need to access external variables defined in one source file from another source file, you can declare them using the extern keyword.