A global variable has scope throughout the entire program, which means it can be accessed and modified from any function or block of code within that program. This visibility allows for data sharing between different parts of the program, facilitating communication and collaboration between different functions without the need for arguments or return values.
In programming, global variables are typically declared outside of any function or class, making them accessible globally. While this can be advantageous for certain scenarios where multiple functions need to share the same data, it is essential to use global variables judiciously, as they can lead to code that is harder to understand and maintain due to unintended interactions and side effects.
In contrast, local variables are only accessible within the block of code or function where they are defined, limiting their reach to that specific context. Static variables, while retaining their value between function calls, still have a limited scope to the function in which they are declared, unless they are explicitly defined as global. Instance variables are related to specific instances of a class and, therefore, have scope only within the context of that class instance.
Thus, global variables, by their nature, provide access throughout the entire program, making them the correct choice in this context.