How using global variables can have implications on the design, maintainability, and test-ability of C# code: Harder to understand and reason about the code: class Program { public static int globalCounter = 0; static void Main() { globalCounter++; Console.WriteLine(globalCounter); } } In this example, the global variable globalCounter is accessible from anywhere in the program, including the Main method. It's not clear where the value of the globalCounter is updated, it could be updated in other methods or classes, making it harder to trace the flow of data and understand the source of bugs. More prone to errors: class Program { public static string globalString; static void Main() { globalString = "Hello" ; Method1(); Method2(); } static void Method1() {