In cpp, two double value in input 2.0 and4.0 but i need answer 6.0 but i get 6.why?

Question

#include<iostream>
using namespace std;
int main()
{
double a=2.0,b=4.0,sum;

sum=a+b;
cout<<sum;

}

Answer 1

hey Abhishek Kumar
We can print float numbers with fixed number of decimal places using std::fixed and std::setprecision, these are the manipulators, which are defined in the iomanip header file.

cout<<fixed<<std::setprecision(1)<<sum;

Answer 2

As the sum of 2.0 and 4.0 doesn't really have a decimal part, C++ only displays 6.

To display the decimal part also, use the 'std::showpoint' manipulator. Like so
`cout << showpoint << a + b;`

Note that the 'showpoint' manipulator will be turned on for the rest of the program till you turn it off. So if you do
```
double a = 2.0, b = 4.0;
cout << showpoint;
cout << a; // decimals displayed
cout << b; // decimals displayed
```
To turn it off, use the 'noshowpoint' manipulator

More info here
https://www.cplusplus.com/reference/ios/showpoint/

EDIT:
When you use 'showpoint', the decimal part is displayed with multiple 0s, not a single 0. You can use the std::setprecision manipulator in the <iomanip> header file to limit the precision to 1 decimal point
https://www.cplusplus.com/reference/iomanip/setprecision/

Answer 3

You can see this :

#include <iostream>
#include<iomanip>
using namespace std;

int main() {
double a = 2.0, b = 2.0,sum;
sum = a + b;
cout << showpoint;
cout << fixed;
cout << setprecision(1);
cout << sum;
return 0;
}