1. Write a portable program using do-while that uses getchar to accept a string of letters in either case from the keyboard and then reverses the case of the string. The program must be independent of...

1. Write a portable program using do-while that uses getchar to accept a string of letters in either case from the keyboard and then reverses the case of the string. The program must be independent of the character set used by the machine.

2. Develop a program using while (outer loop) and for (inner loop) to print all prime numbers between two integers that are input by the user. The program must repeatedly prompt for the pair of integers until the user keys in at least one zero.