Programming in C

94 Chapter 6 Making Decisions
number. Find out what happens in such a case and then modify the program so
that negative numbers are correctly handled. For example, if the number –8645 is
typed in, the output of the program should be 5468–.
6. Write a program that takes an integer keyed in from the terminal and extracts and
displays each digit of the integer in English. So, if the user types in 932, the program
should display
nine three two
Remember to display “zero” if the user types in just a 0. (Note: This exercise is a
hard one!)
7. Program 6.10 has several inefficiencies. One inefficiency results from checking
even numbers. Because it is obvious that any even number greater than 2 cannot
be prime, the program could simply skip all even numbers as possible primes and
as possible divisors.The inner for loop is also inefficient because the value of p is
always divided by all values of d from 2 through p–1.This inefficiency could be
avoided by adding a test for the value of isPrime in the conditions of the for
loop. In this manner, the for loop could be set up to continue as long as no divisor
was found and the value of d was less than p. Modify Program 6.10 to incorporate
these two changes.Then run the program to verify its operation. (Note: In
Chapter 7, you discover even more efficient ways of generating prime numbers.)