Floating-point numbers hold values with a decimal point, so you can represent fractional as well as integral values.
The following are examples of floating-point values:
1.6 0.00008 1234.899 100.0
The last constant is integral, but it will be stored as a floating-point value.
Floating-point numbers are often expressed as a decimal value multiplied by some power of 10, where the power of 10 is called the exponent.
For example, each of the examples of floating-point numbers above could be expressed as shown in Table 2-6.
| Value | With an exponent | Can also be written in C as |
|---|---|---|
| 1.6 | 0.16 x 101 | 0.16E1 |
| 0.00008 | 0.8 x 0.0001 | 0.8E-4 |
| 1234.899 | 0.1234899 x 10000 | 0.1234899E4 |
| 100.0 | 1.0 x 100 | 1.0E2 |
Floating-point variable types only store floating-point numbers.
You have a choice of three types of floating-point variables.
| Keyword | Number of bytes | Range of values |
|---|---|---|
| float | 4 | +/-3.4E+/-38 (6 to 7 decimal digits precision) |
| double | 8 | +/-1.7E+/-308 (15 decimal digits precision) |
| long double | 12 | +/-1.19E+/-4932 (18 decimal digits precision) |
You declare a floating-point variable in a similar way to an integer variable.
float radius; double biggest;
To write a constant of type float, append an f to the number to distinguish it from type double.
You could initialize the previous two variables when you declare them like this:
float radius = 2.5f; double biggest = 123E30;
To specify a long double constant, you append an uppercase or lowercase letter L.
long double huge = 1234567.89123L;