Programming in C

60 Chapter 5 Program Looping

Program 5.8 Reversing the Digits of a Number

// Program to reverse the digits of a number

#include <stdio.h>

int main (void)

{

int number, right_digit;

printf ("Enter your number.\n");

scanf ("%i", &number);

while ( number != 0 ) {

right_digit = number % 10;

printf ("%i", right_digit);

number = number / 10;

}

printf ("\n");

return 0;

}

Program 5.8 Output

Enter your number.

13579

97531

Each digit is displayed as it is extracted by the program. Notice that you did not include

a newline character inside the printfstatement contained in the whileloop.This forces

each successive digit to be displayed on the same line.The final printfcall at the end of

the program contains just a newline character, which causes the cursor to advance to the

start of the next line.

The doStatement

The two looping statements discussed so far in this chapter both make a test of the con-

ditions beforethe loop is executed.Therefore, the body of the loop might never be exe-

cuted at all if the conditions are not satisfied.When developing programs, it sometimes

becomes desirable to have the test made at the endof the loop rather than at the begin-

ning. Naturally, the C language provides a special language construct to handle such a

situation.This looping statement is known as the dostatement.The syntax of this state-

ment is as follows: