In computing, 'real number' often refers to non-complex floating-point numbers.It 

include both rational numbers, such as 42 and 3/4, and irrational numbers such 

as pi = 3.14159265...

When the accuracy of the floating point number is insufficient, we can use the doubleto 

define the number. The double is same as float but with longer precision and takes double 

space (8 bytes) than float.

To extend the precision further we can use long double which occupies 10 bytes of memory

 space.