Calculator in division operation using C [closed] - c

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Closed 9 years ago.
I am making a calculator using C language. But the problem is that I am stuck in division.
I want that when I input 0 divided by 0, it will print undefined and if a number divided by zero will print cannot be divide by zero (which seems I got this).
Here is my code:
#include <stdio.h>
#include <math.h>
main(){
float num1, num2, total;
int a;
char choice;
clrscr();
printf("What operation you want to perform?\n 1. Addition\n 2. Subtraction\n 3. Multiplication\n 4. Division\n");
scanf("%d", &a);
switch(a) {
case 1: //Addition
printf("Addition\n Enter two numbers to be added\n");
scanf("%f%f",&num1, &num2);
total=num1 + num2;
printf("\nThe total is: %f + %f = %f\n", num1, num2, total);
printf("\nDo want to continue? Y or N: ");
scanf("%s", &choice);
if(choice=='y'||choice=='Y')
main();
else
exit(1);
break;
case 2: //Subtraction
printf("Subtraction\n Enter two numbers to be subtract\n");
scanf("%f%f", &num1, &num2);
total=num1 - num2;
printf("\nThe Difference is: %f + %f = %f\n", num1, num2, total);
printf("\nDo you want to continue? Y or N: ");
scanf("%s", &choice);
if(choice=='y'||choice=='Y')
main();
else
exit(1);
break;
case 3: //Multiplication
printf("Multiplication\n Enter two numbers to be multiplied\n");
scanf("%f%f",num1, num2);
total=num1*num2;
printf("\nThe product is: %f * %f = %f\n", num1, num2, total);
printf("\nDo you wish to continue? Y or N: ");
scanf("%s", &choice);
if(choice=='y'||choice=='Y')
main();
else
exit(1);
break;
case 4: //Division
abcd:
printf("Division\n Enter two numbers to be divide\n");
scanf("%f%f",&num1, &num2);
if(num2==0.0)
{ printf("\n %f cannot be divided by zero\n\n", num1); // ;(
goto abcd;}
else if(num1==0.0 && num2==0.0) //This is my problem here.
{printf("\nIts Undefined. 0 / 0\n\n ");
}
total=num1/num2;
printf("\nThe qoutient is %f / %f = %f\n", num1, num2, total);
printf("\nDo you want more? Y or N: ");
scanf("%s", &choice);
if(choice=='y'||choice=='Y')
main();
else
exit(1);
break;
default:
printf("Can you add letters? LOL only numbers");
printf("\nDo you want to continue? Y/N ");
scanf("%s", &choice);
if(choice=='y'||choice=='Y')
main();
else
exit(1);
break;
}
getch();
}

Answer 1

You have:
if(num2==0.0)
// division by zero
else if(num1==0.0 && num2==0.0)
// zero/zero is undefined
The problem is that if both numbers are 0.0, it's caught by the first test, and the second is never executed.
You need to test for both numbers being zero first, and then check whether the second number is zero.
Or you can combine the two tests:
if (num2 == 0.0) {
if (num1 == 0.0) {
// zero / zero
}
else {
// non-zero / zero
}
}
else {
// ok
}

Answer 2

Your if else statements are not ordered correctly.
Always try to put the case that is most specific before the more general cases.
So in your case, the specific case is when num1 == 0.0 && num2 == 0.0
Whereas the general case is num2 == 0.0
Also, your program would crash when both num1 and num2 are zero, seeing as it divides them anyway in that case.