Question

Why can't I get a decimal number in C++?

So there's a question in my textbook.

number = (1/3) * 3;

cout << "(1/3) * 3 is equal to " << number;

the answer should be 0.99999...

While in the C++,

when I declared the variable number as integer. The output answer is 0. I got it because it won't calculate the decimal unless I told the program.

So I declared it again as double. The output is 1.

Then, I changed 1/3 to 1.0/3. (my textbook said if one number is int and another number is double, the output will be double )

However, my output is still 1.

Then, I declared it as double and changed the whole as (1.0/3.0)*3.0

The answer is still 1.

How can I get the 0.9999999999999... or 0.9(at least it approximate than 1)

Answer 1

It is because (1/3)*3 is equal to 1. You can even try it on the calculator.

(1/3)*3 =3 which is recurring decimal or non-terminating decimal number 0.9999...

If you want to specify the number of decimal digits in the output, you can do it by the function setprecision(int n) where n is the number of digits you want. You will also need to declare an additional header file - #include<iomanip>.

Example-

#include <iostream>
#include<iomanip>

using namespace std;

int main()
{
float number = (1.0/3);
cout<<setprecision(2)<<number<<endl;
cout<<setprecision(3)<<number;

return 0;
}

The output would be-

0.33
0.333