Simple calculator program in C - c

Question

I need to write a simple program in C that makes simple calculations of: +,-,*,/
Now, I am using Visual Studio Express 2013, and here is the code:
#include <stdio.h>
#include <stdlib.h>
int main(){
double a, b;
double sum = 0;
char o; //operator
printf("Enter operator\n");
scanf_s("%c", &o);
printf("Enter first operand\n");
scanf_s("%f", &a);
printf("Enter second operand\n");
scanf_s("%f", &b);
if (o == '+'){
sum = a + b;
printf("The result is", &sum);
}
if (o == '-'){
sum = a - b;
printf("The result is", sum);
}
if (o == '*'){
sum = a*b;
printf("The result is", sum);
}
if (o == '/'){
if (b == !0){
sum = a / b;
printf("The result is", sum);
}
else printf("Error");
}
getchar();
}
My output: Enter operator
+
Enter first operand
3.5
Enter second operand
5.4
And after I type the second number- the program exits, and nothing!
There are no compilation errors, and I have no idea what to do. Can someone help, please?

Answer 1

You're not using printf correctly. This is what you're using.
printf("The result is", &sum);
You're not specifying the type of output in the format string, and you're passing the address of the variable you want to print, not the value.
You should use:
printf("The result is %lf\n", sum);
%lf is specifying that you want to print a double, \n adds a newline, and you pass the value of the variable sum, not it's address.
Also, you should change if (b == !0){ to if (b != 0){. If you leave what you put, it's the equivalent to if (b == 1){, which probably isn't what you want.
EDIT Here is the code, with my modifications, which gives correct results. I'll indicate which lines I changed
#include <stdio.h>
#include <stdlib.h>
int main(){
double a, b;
double sum = 0;
char o; //operator
/* I had to use scanf, since I'm not using MS/Visual Studio, but GCC */
printf("Enter operator\n");
scanf("%c", &o);
printf("Enter first operand\n");
scanf("%lf", &a); /* changed %f to %lf */
printf("Enter second operand\n");
scanf("%lf", &b); /* changed %f to %lf */
/* I prefer to use if ... else if ..., this is personal preference */
if (o == '+'){
sum = a + b;
printf("The result is %lf\n", sum); /* Changed, see original post */
} else if (o == '-'){
sum = a - b;
printf("The result is %lf\n", sum); /* Changed, see original post */
} else if (o == '*'){
sum = a*b;
printf("The result is %lf\n", sum); /* Changed, see original post */
} else if (o == '/'){
if (b != 0){
sum = a / b;
printf("The result is %lf\n", sum); /* Changed, see original post */
}
else printf("Error");
}
getchar();
return 0;
}

Answer 2

You are using %f format to read doubles. You should use %lf:
scanf_s("%lf", &a);
The print methods actually don't print the result (format is incomplete). And, instead of the value, you are passing variable's address. It should be:
printf("The result is %e", sum);
You should also change if (b == !0) to if (b != 0)

Answer 3

Now it's working fine I made some changes to it
the problem was with ur "scanf_s" and "%f" go throw with it
#include<stdio.h>
#include<stdlib.h>
int main(){
double a, b;
double sum = 0;
char o; //operator
printf("Enter operator\n");
scanf("%c", &o);
printf("Enter first operand\n");
scanf("%d", &a);
printf("Enter second operand\n");
scanf("%d", &b);
if (o == '+'){
sum = a + b;
printf(" The result is %d", sum);
}
if (o == '-'){
sum = a - b;
printf("The result is %d", sum);
}
if (o == '*'){
sum = a*b;
printf("The result is %d", sum);
}
if (o == '/'){
if (b == !0){
sum = a / b;
printf("The result is %d", sum);
}
else printf("Error");
}
getchar();
}