#include <stdio.h>

int i1, i2;

/*function declaration */

int add(int op1, int op2);
int sub(int op1, int op2);
int mul(int op1, int op2);
int div(int op1, int op2);
void printMenu();
void getInput();
void outputResult(int n);


int main(void)
{
	int j, choice = 1;

/*	printMenu();
	scanf();*/

	while(choice != 0)
	{
		printMenu();
		scanf("%d", &choice);
		switch(choice)
		{
		case 1: getInput();
			j = add(i1, i2);
			outputResult(j);
			break;

		case 2: getInput();
			j = sub(i1, i2);
			outputResult(j);
			break;
 
		case 3: getInput();
			j = mul(i1, i2);
			outputResult(j);
			break;
 
		case 4: getInput();
			j = div(i1, i2);
			outputResult(j); 
			break;

		default: break; 
		}
	}
	return 0;
}

int add(int op1, int op2)
{
	int r;
	r = op1 + op2;
	return r;
}

int sub(int op1, int op2)
{
	int r;
	r = op1 - op2;
	return r;
}

int mul(int op1, int op2)
{
	int r;
	r = op1 * op2;
	return r;
}

int div(int op1, int op2)
{
	int r;
	if(op2 == 0)
	{
		printf("   	invalid divisor 0!!!! \n");
		return -999999999;
	}
	r = op1 / op2;
	return r;
}

void printMenu()
{
	printf("   1. add two numbers \n");
	printf("   2. subtract two numbers \n");
	printf("   3. multiple two numbers \n");
	printf("   4. divide two numbers \n");
	printf("   0. exit \n");
	printf("   Enter your choice: ");
}
void getInput()
{
	printf("   	i1 = ");
	scanf("%d", &i1);

	printf("   	i2 = ");
	scanf("%d", &i2);
}

void outputResult(int n)
{
	printf("   	The result is %d \n", n);
	printf("********************************\n\n");
}