Follow these steps:

1. Create a file named constant.rs with the next code snippet.

2. Declare the global UPPERLIMIT using constant:

        // Global variables are declared outside scopes of other 
        function
        const UPPERLIMIT: i32 = 12;

3. Create the is_big function by accepting a single integer as input:

        // function to check if bunber 
        fn is_big(n: i32) -> bool {
          // Access constant in some function
          n > UPPERLIMIT
        }

4. In the main function, call the is_big function and perform the decision-making statement:

        fn main() {
          let random_number = 15;

          // Access constant in the main thread
          println!("The threshold is {}", UPPERLIMIT);
          println!("{} is {}", random_number, if
          is_big(random_number) { "big" } else { "small"
          });

          // Error! Cannot modify a `const`.
          // UPPERLIMIT = 5;

        }

You should get the following screenshot as output upon running the preceding code: