C Tutorial  Floating point types  
Introduction to C language Integer types Char constants Int constants Type combination and promotion Int overflow Floating point types Comments Variables Assignment operator Truncation Int vs float arithmatic Mathematical operators Unary Increment Operators Pre and Post Variations C Programming Cleverness and Ego Issues Relational Operators Logical Operators Bitwise Operators Other Assignment Operators

Floating point Types
long double Possibly even bigger floating point number (somewhat obscure) Constants in the source code such as 3.14 default to type double unless the are suffixed with an 'f' (float) or 'l' (long double). Single precision equates to about 6 digits of precision and double is about 15 digits of precision. Most C programs use double for their computations. The main reason to use float is to save memory if many numbers need to be stored. The main thing to remember about floating point numbers is that they are inexact. For example, what is the value of the following double expression?
(1.0/3.0 + 1.0/3.0 + 1.0/3.0) // is this equal to 1.0 exactly? The sum may or may not be 1.0 exactly, and it may vary from one type of machine to another. For this reason, you should never compare floating numbers to eachother for equality (==)  use inequality (<) comparisons instead. Realize that a correct C program run on different computers may produce slightly different outputs in the rightmost digits of its floating point computations.

