Thread: problems with loops

I was trying to write a simple program to convert a number to its hexidecimal equivalent. Easy enough, I got that much. The problem comes in when I want it to loop, depending on the user's answer to the last question, either y (for yes, and to continue the loop) or anything else to end the program.

Here's my coding so far:

#include <stdio.h>
main ()
{
char answer, number;
answer= 'y';
do{
printf("\nEnter in the number you wish converted to hexidecimal: ");
number = getchar();
Printf("\nThe hexidecimal representation of %c is 0x%00x.", number, number);
printf("\nDo you wish to enter in a new number? Press y for yes, any other key to exit.", answer);
answer = getchar();
}
while (answer='y');

return 0;
}

Any ideas as to what I'm doing wrong here? It's somewhere in the loop, I know that, because it works perfectly fine without the loop.

while answer == 'y'

still not working. It doesn't allow me to input the answer, instead throws me back to the DOS prompt.

The reason why your program is not working is that the getchar gets all characters from input, including the enter key. When you type a number followed by the enter key the second getchar will read the enter (= '\n') and stop the program. It's better to use the gets function to read a complete line:

Code:

#include <stdio.h> 
#include <stdlib.h>
#include <ctype.h>

main () 
{ 
	char line[256];
	int number;

	do{ 
		printf("Enter a number or 'x' to exit\n");
		/* read the complete line */
		gets(line);

		/* check if first character is a digit */
		if(isdigit(line[0]))
		{
			/* convert string-number to integer */
			number = atoi(line);
			printf("The hexidecimal representation of %d is: %x\n", number, number);
		}
		else if(line[0] != 'x')
		{
			printf("Invalid number\n");
		}
	} while(line[0] != 'x');


	return 0; 
}

I knew I could do it with a do-while loop, I just wasn't sure where I was going wrong.