C++ :

Write a program that prompts the user to input a character that is an ASCII letter in the range [A-Za-z]. Your program should print the same letter, but in the opposite case. For example, if the input is B, the program should print b; if the input is g, it should print G. It should print an appropriate error message if the input character is not an upper or lower case letter. Your program should continue asking for input, with appropriate error checking, until the user enters a. Your program must use a function that you write called swapCase (char s) that does the actual conversion process