Declaration statements in C - c

Question

I seem to have a problem with declarations screwing up my math. Any advice or suggestions are highly welcomed.
Here's the code:
int num1, num2, num3, num4, op, ;
op = ((1==num3) || (2==num4));
num3 = (num1 + num2);
num4 = (num1 * num2);
I've been trying lots of arrangements and re-assignments. A lot has compiled, but when 5 + 5 = 2659043, there's a problem...

Answer 1

Not sure what you're trying to do, but this is what your code is doing:
int num1, num2, num3, num4, op, ;
This line informs the C compiler that it needs to allocate space for 5 integers (num1, num2, num3, num4, op), these integers can now be used as variables until the scope expires. Not sure why you have the last ',' you might want to remove that.
op = ((1==num3) || (2==num4));
If num3 is 1, or num4 = 2, then set op to 1 (true). Otherwise, set op to 0 (false).
num3 = (num1 + num2);
Self-explanatory: Add num1 and num2 and put the sum into num3.
num4 = (num1 * num2);
Self explanatory: Multiply num1 and num2 and put the product into num4.
Immediately I see an issue with your program. You are using these variables, but have not initialized them to anything. For example, how is there supposed to be a sum of (num1 + num2) if num1 and num2 do not have a value. Try this:
#include <stdio.h>
int main()
{
int num1, num2, sum;
num1 = 1;
num2 = 2;
sum = num1 + num2;
printf("sum = %d\n", sum);
}

Answer 2

Okay... there's a lot wrong here, but I'll go through what you posted in the comments point by point.
#include <stdio.h>
int main() {
/*Declare the active agents */
int num1=0, num2=0, num3=0, num4=0, op = 1 || 2 ;
You initialize your variables to zero here, except op, which you set to 1 (1 || 2, which is the boolean or, will return 1 (true), so as a result you set op to 1).
num3 = (num1 + num2);
num4 = (num1 * num2);
Here you set num3 and num4 both to zero, since num1 + num2 is 0 + 0 and num1 * num2 is 0 * 0. You want to move this down after your scanf's.
/* Information Extraction Method */
printf("YO MOFO!!!Press a number or hit the dirt!!\n");
scanf("%d", &num1);
printf("Since you didn't hit the dirt, how about another number?\n");
scanf("%d", &num2);
/* Menu (AKA Input */
printf("If you want to add, press 1 ,\nIf you want to multiply, press 2 ... \n\n ");
scanf ("%d", &op);
These printf's and scanf's are good. Good job.
/* PROCESS */
if (op = 1) {num3;};
if (op = 2) {num4;};
Three things here. First, op = 1 is assigning 1 to op. Same with op = 2. You want op == 1 and op == 2 as you have below. The result of this will be that op will always be 2 after these if statements.
The second thing is that, while a valid statement, num3; by itself won't do anything.
Finally, while it doesn't hurt anything, you don't need semicolons after your closing curly braces.
/* OutPut */
if (op == 1) {
printf("Alone, a toothpick is weak, but as part of a sum, your answer is:\n%d"), &num3;
};
if (op == 2) {
printf("Multiplied as a sum of it's parts, your answer is:\n%d"), &num4;
};
Here you're printing out the address of num3 and num4 instead of their values. This is part of the reason you're seeing large numbers that don't make sense, it's the address of num3 and num4 in memory. Only scanf needs the ampersand (&), printf does not. Also, as it stands, the actual value of these will always be 0 since your calculations are done before you get the numbers from the user.
EDIT: Actually, it turns out the reason you aren't getting the right numbers here is that you aren't passing the number to printf at all. You have num3 and num4 outside of the parentheses. There still shouldn't be an ampersand before the variable name, but it should look like this printf("Multiplied... is:\n%d", num4); Notice how num4 is inside the parentheses.
printf("\n\n\n\nMath frum da hud..... Yo. \n\n\nLOL\n >;]");
/* End Of Program */
return 0;
}
Edit: For clarity's sake, I've re-written it in a manner such that it should work the way you intended.
#include <stdio.h>
int main() {
/*Declare the active agents */
int num1=0, num2=0, num3=0, num4=0, op = 0;
/* Information Extraction Method */
printf("YO MOFO!!!Press a number or hit the dirt!!\n");
scanf("%d", &num1);
printf("Since you didn't hit the dirt, how about another number?\n");
scanf("%d", &num2);
num3 = (num1 + num2);
num4 = (num1 * num2);
/* Menu (AKA Input */
printf("If you want to add, press 1 ,\nIf you want to multiply, press 2 ... \n\n ");
scanf ("%d", &op);
/* OutPut */
if (op == 1) {
printf("Alone, a toothpick is weak, but as part of a sum, your answer is:\n%d", num3);
};
if (op == 2) {
printf("Multiplied as a sum of it's parts, your answer is:\n%d", num4);
};
printf("\n\n\n\nMath frum da hud..... Yo. \n\n\nLOL\n >;]");
/* End Of Program */
return 0;
}
HTH.

Answer 3

You did not initialize the variables, so their values are undefined (and probably not 0). You should initialize (like that, for example):
int num1 = 0, num2 = 0, num3 = 0, num4 = 0, op = 0 ;