if statement not working properly? [closed] - c

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When i run the program, if i enter 0 for the "d" option, it doesn't print what i set the if statement to print when a 0 is entered as u can see almost at the end of the program. The comments in this program are part of the program i just made it like this so you can see the code that is not in comment form is my problem.
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
main()
{
// David Brand
int result, num, num1, calc, calc1, mark;
char A1, A2, ch;
float num2, num3, result1;
printf("\n\n\tMenu");
printf("\n\n\ta. Addition");
printf("\n\tb. Subtraction");
printf("\n\tc. Multiplication");
printf("\n\td. Division");
printf("\n\n\tSelect a, b, c or d: ");
ch = getch();
if (ch == 'a')
{
printf("\n\n\tEnter a number ");
scanf("%d", &num);
printf("\n\n\tEnter another number ");
scanf("%d", &num1);
printf("\n\n\tPlease add the two numbers ");
scanf("%d", &result);
if (result == num + num1)
printf("\n\n\tCorrect");
if (result != num + num1)
printf("\n\n\tWrong");
}
if (ch == 'b')
{
printf("\n\n\tEnter a number ");
scanf("%d", &num);
printf("\n\n\tEnter another number ");
scanf("%d", &num1);
printf("\n\n\tPlease subtract from the first number ");
scanf("%d", &result);
if (result == num - num1)
printf("\n\n\tCorrect");
if (result != num - num1)
printf("\n\n\tWrong");
}
if (ch == 'c')
{
printf("\n\n\tEnter a number ");
scanf("%d", &num);
printf("\n\n\tEnter another number ");
scanf("%d", &num1);
printf("\n\n\tPlease multiply the two ");
scanf("%d", &result);
if (result == num * num1)
printf("\n\n\tCorrect");
if (result != num * num1)
printf("\n\n\tWrong");
}
if (ch == 'd')
{
printf("\n\n\tEnter a number ");
scanf("%f", &num2);
if (num2 != 0)
printf("\n\n\tEnter another number ");
scanf("%f", &num3);
printf("\n\n\tPlease divide the two numbers ");
scanf("%f", &result1);
if (num2 == 0)
printf("\n\n\tZero divisor");
printf("\n\tHit a key to end the program");
getch();
system("cls");
exit(0);
}
if (result1 == num2 / num3)
printf("\n\n\tCorrect");
if (result1 != num2 / num3)
printf("\n\n\tWrong");
getch();
system("cls");
}

Answer 1

Change your code to
if(ch=='d')
{
printf("\n\n\tEnter a number ");
scanf("%f", &num2);
if(num2==0)
{
printf("\n\n\tZero divisor");
printf("\n\tHit a key to end the program");
getch();
system("cls");
exit(0);
}
else if(num2!=0)
{
printf("\n\n\tEnter another number ");
scanf("%f", &num3);
printf("\n\n\tPlease divide the two numbers ");
scanf("%f", &result1);
}
}

Answer 2

Here is that section of code after running through auto-layout:
if(ch=='d')
{
printf("\n\n\tEnter a number ");
scanf("%f", &num2);
if(num2!=0)
printf("\n\n\tEnter another number ");
scanf("%f", &num3);
printf("\n\n\tPlease divide the two numbers ");
scanf("%f", &result1);
if(num2==0)
printf("\n\n\tZero divisor");
printf("\n\tHit a key to end the program");
getch();
system("cls");
exit(0);
}
It doesn't print anything after you enter 0 because it falls straight through to another scanf. If you want more than one statement to be conditionally executed with if, you need to enclose those statements in curly brackets.
I expect you wanted something like this:
if(ch=='d')
{
printf("\n\n\tEnter a number ");
scanf("%f", &num2);
if(num2!=0) {
printf("\n\n\tEnter another number ");
scanf("%f", &num3);
printf("\n\n\tPlease divide the two numbers ");
scanf("%f", &result1);
} else {
printf("\n\n\tZero divisor");
printf("\n\tHit a key to end the program");
getch();
system("cls");
exit(0);
}
}

Answer 3

I don't have a c compiler at work but I think this should fix most of the issues your having
Also don't you need to check for num3 to be 0 not num2? 0 / 5 is fine 5 / 0 is not
You don't need to check for == and then immediately check for != you know from the == that the opposite of that using else is !=
You should be able to input the two numbers or even the answer as well into a single line to make it easier on the user using a single scanf line also you could make part of this into functions as there is alot of repeated code
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
main()
{
//David Brand
int result,num,num1,calc,calc1,mark;
char A1,A2,ch;
float num2,num3,result1;
printf("\n\n\tMenu");
printf("\n\n\ta. Addition");
printf("\n\tb. Subtraction");
printf("\n\tc. Multiplication");
printf("\n\td. Division");
printf("\n\n\tSelect a, b, c or d: ");
ch=getch();
if(ch=='a')
{
printf("\n\n\tEnter two numbers separated by a space i.e. 5 7");
scanf("%d %d", &num, &num1);
printf("\n\n\tPlease add the two numbers ");
scanf("%d", &result);
if (result == num + num1)
printf("\n\n\tCorrect");
else
printf("\n\n\tWrong");
}
else if(ch=='b')
{
printf("\n\n\tEnter two numbers separated by a space i.e. 5 7");
scanf("%d %d", &num, &num1);
printf("\n\n\tPlease subtract from the first number ");
scanf("%d", &result);
if(result == num-num1)
printf("\n\n\tCorrect");
else
printf("\n\n\tWrong");
}
else if(ch=='c')
{
printf("\n\n\tEnter two numbers separated by a space i.e. 5 7");
scanf("%d %d", &num, &num1);
printf("\n\n\tPlease multiply the two ");
scanf("%d", &result);
if(result == num * num1)
printf("\n\n\tCorrect");
else
printf("\n\n\tWrong");
}
else if(ch=='d')
{
printf("\n\n\tEnter two numbers separated by a space i.e. 5.7 7.5");
scanf("%f %f", &num2, &num3);
if(num3 == 0)
{
printf("\n\n\tZero divisor");
}
else
{
printf("\n\n\tPlease divide the two numbers ");
scanf("%f", &result1);
if(result1 == (num2 / num3))
printf("\n\n\tCorrect");
else
printf("\n\n\tWrong");
}
}
printf("\n\tHit a key to end the program");
getch();
exit(0);
}