Understanding Floating Point

Unlike integers, floating-point variable can hold wide range of values, including fractions and real numbers. For instance, 3.14, -0.1 etc.

The term floating-point in floating point numbers refers to the dynamic positioning of the decimal point, allowing a variable number of digits before and after it.

There are three different floating point data types: float, double, and long double. These types differ in the precision they offer and are used to represent real numbers in the program. As with integers, C++ does not define the actual size of these types but it does specify minimum size requirements.

• Floating point data types are always signed (can hold positive, negative values, and 0).

Syntax for Declaring Floating-Point Variables:

Declaring a floating-point variable in C++ follows a straightforward syntax. You specify the data type (float, double, or long double), followed by the variable name and an optional initialization.

float myFloat;
double myDouble;
long double myLongDouble;

If you wish to initialize the variable at the time of declaration, you can do so as follows:

float piFloat = 3.14f;  // 'f' suffix indicates a float literal
double piDouble = 3.14159;
long double piLongDouble = 3.141592653589793238L;  // 'L' suffix indicates a long double literal

Note that by default, floating point literals default to type double. An f suffix is used to denote a literal of type float. As shown in the example above – suffixes like f for float and l for long double ensure that the literal is interpreted as the correct type.

Initialization and Default Values:

float uninitializedFloat;  // Uninitialized variable - content is indeterminate
float initializedFloat = 0.0f;  // Initialized to 0.0

double uninitializedDouble;  // Uninitialized variable - content is indeterminate
double initializedDouble = 0.0;  // Initialized to 0.0

long double uninitializedLongDouble;  // Uninitialized variable - content is indeterminate
long double initializedLongDouble = 0.0L;  // Initialized to 0.0

Printing floating point numbers

Consider the following program:

#include <iostream>

int main()
{
	std::cout << 5.0 << '\n';
	std::cout << 6.7f << '\n';
	std::cout << 9876543.21 << '\n';

	return 0;
}

// Output
5
6.7
9.87654e+06

In the first case, the std::cout printed 5, even though we typed in 5.0. By default std::cout will not print the fractional part of a number if the fractional part is 0.

In the second case, the number prints as we expect.

In the third case, it printed the number in scientific notation.