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C++ Data Types

Double-Precision Numbers

The precision of float (7 decimal digits) is not always enough. But C++ has a solution: double. With a precision of 15 decimal digits, it is much more accurate than float. The syntax of using double is the same as always:

double


              1
            
double num = 3.14159265359;

By default, cout prints floating-point numbers with a precision of 6 significant digits. That way, you won't see a difference between float and double. To set a larger precision, we can use std::cout << std::setprecision(15); again (this will set the precision to 15 significant digits).

Don't forget to include <iomanip> to be able to use std::setprecision().

main


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#include <iostream>
#include <iomanip>

int main()
{
  	float pi_float = 3.14159265358979;
	double pi_double = 3.14159265358979;
	
    std::cout << "float pi: " << pi_float << std::endl;
    std::cout << "double pi: " << pi_double << std::endl;
    
    std::cout << std::setprecision(15);
    std::cout << "float pi with setprecision: " << pi_float << std::endl;
    std::cout << "double pi with setprecision: " << pi_double << std::endl;
}

How is better precision achieved in `double`?

It just takes up more memory. A float type takes up 4 bytes, and a double takes up 8 bytes of memory.

There also is a long double type. Its size ranges from 8 bytes (just like a double) to 16 bytes. You can check the size of the long double on your system by using the following code:

sizeof


              1
            
std::cout << sizeof(long double);

Additionally, you should add L to a value you are assigning (otherwise, the value will be assigned with the precision of double). Look at the example:

double


              1
            
long double pi = 3.141592653589793238462643L;

Note

If you got zeros in the output, make sure you assigned the values exactly like shown above (1/3., 1/3.L).

Завдання

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You need to calculate (1/3)² using different data types. For that, assign the value of 1/3 to the float, double, and long double typed variables. Then print those numbers multiplied by themselves.

Initialize a float variable with the value 1/3.;
Initialize a double variable with the value 1/3.;
Initialize a long double variable with the value 1/3.L.
note: long double takes up 16 bytes of memory on our system
Set the precision of output to 25 decimals with setprecision(25);
Print all those values multiplied by themselves.

Перейдіть на комп'ютер для реальної практикиПродовжуйте з того місця, де ви зупинились, використовуючи один з наведених нижче варіантів

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Секція 2. Розділ 5

Double-Precision Numbers

double


              1
            
double num = 3.14159265359;

Don't forget to include <iomanip> to be able to use std::setprecision().

main


              123456789101112131415
            
#include <iostream>
#include <iomanip>

int main()
{
  	float pi_float = 3.14159265358979;
	double pi_double = 3.14159265358979;
	
    std::cout << "float pi: " << pi_float << std::endl;
    std::cout << "double pi: " << pi_double << std::endl;
    
    std::cout << std::setprecision(15);
    std::cout << "float pi with setprecision: " << pi_float << std::endl;
    std::cout << "double pi with setprecision: " << pi_double << std::endl;
}

How is better precision achieved in `double`?

It just takes up more memory. A float type takes up 4 bytes, and a double takes up 8 bytes of memory.

There also is a long double type. Its size ranges from 8 bytes (just like a double) to 16 bytes. You can check the size of the long double on your system by using the following code:

sizeof


              1
            
std::cout << sizeof(long double);

Additionally, you should add L to a value you are assigning (otherwise, the value will be assigned with the precision of double). Look at the example:

double


              1
            
long double pi = 3.141592653589793238462643L;

Note

If you got zeros in the output, make sure you assigned the values exactly like shown above (1/3., 1/3.L).

Завдання

Swipe to show code editor

Initialize a float variable with the value 1/3.;
Initialize a double variable with the value 1/3.;
Initialize a long double variable with the value 1/3.L.
note: long double takes up 16 bytes of memory on our system
Set the precision of output to 25 decimals with setprecision(25);
Print all those values multiplied by themselves.

Все було зрозуміло?

Дякуємо за ваш відгук!

Секція 2. Розділ 5

C++ Data Types

Double-Precision Numbers

How is better precision achieved in double?

Double-Precision Numbers

How is better precision achieved in double?

How is better precision achieved in `double`?

How is better precision achieved in `double`?