#include <stdio.h>
#include <ctype.h>
void calculator();

int main()
{
	
	int ch, choose = 0, sumCh;/* choose = the choice of the user, sumCh = how many charcters did the user typrd*/
	while (choose!=2)/*stop the loop whaen the user types 2*/
	{
		printf("select from the following:\n 1.calculate an equation\n 2. stop\n");
		for(sumCh = 0;(ch = getchar())!='\n';)
		{
			if (ch!=' ')/*counts the characters*/
				sumCh++;
			if (ch == '1')/*the user wants to calculate an equation*/
				choose = 1;
			else if (ch == '2')/*the user wants to get out from the loop*/
				choose = 2;
			else/*the user entered an ilegal input*/
				choose = 10;
		}
		if (sumCh == 1)/*checks if the user typed only 1 character(legal)*/
		{
			if (choose == 1)/*calculate the equation if the user typed 1*/
			{
				calculator();
				choose = 0;
			}
			else/*prints error if the user entered an illegal number*/
			{
				if (choose!=2)
					printf("\nError, illegal input, try again\n");
			}
		}
		else/*if the user typed more than one character*/
		{
			printf("\nError, illegal input, try again\n");
			choose = 0;
		}
	}
	return 0;
}