converting float to integer

[biradam]

i wrote a program for practice. There is no problem with codes and program runs without giving any error. However, when there is a problem about output.

I tried to rounded the floating number just considering their 2 digits after the decimal points. The program should round up the number if the decimal is .45 or higher and round down the number if the decimal is less than .45 . In general, there is no problem about the outputs, but when the input is 64.45 , 65.45 , 66.46, etc. the number doesn't rounded up; it is rounded down.

The code of program is

#include<iostream>
#include<math.h>

using namespace std;

int main()
{
	float gr;
	int x;
	float a;
	cout << "enter grade: ";

	cin >> gr;
	a = 100 * gr;

	cout << a << endl;
	x = a;
	cout << x << endl;
	x = x % 100;
	cout << x << endl;
	if (x % 100 <= 44)
			{
				gr= floor(gr);
			}
			else
			{
				gr=ceil(gr);
			}
	cout << gr << endl;

	return 0;


}

p.s : when i changed if statement as if ( x % 100 <= 48) the problem was again when the input is 64.45,65.45,etc.

p.s2 : there is no problem when the input is 63.45 or less.

p.s3 :
I get a and x as outputs deliberately, in order to see where the problem is.

When the input is 63.45

output:
6345
6345
45
64


But when the input is 64.45

output:
6545
6544
44
65

where first one is output of "a" and second one is output of "x"

[D80DSL3A]

I'd guess it's because floats aren't exact in how they represent the number. Probably 64.45 gets represented as 64.44999.. then 100*gr becomes 6444.999 and x = 6444 results. I fixed it by using the ceil() earlier.
Try replacing line 17 in your code with this:
x = (int)ceil(a);

[AaronZim]

What you need to understand type casting to solve this problem. To change a float to a int works like this:

#include<iostream>
#include<math.h>

using namespace std;

int main()
{
	float gr;
	float a;
	cout << "enter grade: ";
	cin >> gr;

	a = gr - (int)gr; //a = value right of the decimal

	if (a >= 0.45) //round up
		gr += 1.0f - a; //add the difference to make the decimal value of gr whole.
	else
		gr -= a; // remove decimal value. could also read gr = (int)gr;
	cout << "Your final grade is: " << x << endl;
	return 0;
}

To further understand:
a = gr - (int)gr;
You should also see that it is the same as:
a = gr - (float)(int)gr;
As a float can only do math with another float so the (float) operation is included by the the interpreter, I just removed it for cleanliness.

I hope this helps.