👉 In computer programming, a "unfillable" variable is a variable that can be assigned to null or undefined values, but cannot be used for any other purpose. This means that if you try to assign a value to a "unfillable" variable, it will not compile and cause an error. For example: ```c int x = 0; x = 5; // Compile error ``` In this case, the compiler will check if `x` is null or undefined before
