Thread: Using putchar to output an integer with more than 1 digit

Hi, I'm trying to create a program that does simple C arithmetic calculations (such as 12 + 12). There can be multiple blanks before and after an operand. The expression and result is supposed to be displayed like 12+12=24, where the expression (12+12) must be output from only using putchar. The = and result (24) can be used with a printf function, but anything dealing with the expression can not be used with printf (putchar only.) So far, I just want to know how I can store the operand (12 for example) and output it.

Code:

#include <stdio.h>

int convert(void);

int main(void)
{
	int op1;
	op1 = convert();

	printf("%d", op1);

	return 0;

}


int convert(void)
{
	int iochar,
		sum = 0;
	while(((iochar = getchar() ) != ' ' ) && (iochar != '\n' ) )
	{
		sum = sum * 10 + (iochar - '0');
	}
	return (sum);
}

The code I have above was used mostly from a convert function from my programming book which reads from standard input until either a blank or end of line is found. It works, but only because printf function is being used in main. If I enter something such as putchar(op1); instead of printf("%d", op1);, I get some awkward results (symbols, alt codes, etc.) Any advice would be highly appreciated, I just want to know how I can store the integer (with more than 1 digit) using getchar and also output it using putchar. I've also tried tackling the problem with a different piece of code, but only the first number of the operand would be output (instead of 12, it would only output 1.)

You can put your putchar in the while loop to re-echo that to the scree, but your user has already written that to the screen, why would you want to do it again?

Actually, I think I just found out exactly what to do. Hopefully. Thanks for anyone trying to answer my question, using getchar/putchar gets to my head.