The program consists of two functions:
concatenate_strings: This function takes two string references as input and returns a new String by concatenating them. It uses the push_str method to append the contents of the first string and the second string to the result.
main: This is the entry point of the program. It initializes two string variables, string1 and string2, with the desired values. It then calls the concatenate_strings function with the references to string1 and string2 as arguments. The result is stored in a variable called concatenated_string. Finally, it prints the concatenated_string to the console.
Feel free to modify the values of string1 and string2 in the main function to see different concatenation results.