There are many different types of data types in C++. floating point data types are for things that need the decimal point to 'float' around, like for use in scientific calculations, or other things that need to be for decimal math. the Int, or integer, data type is used for whole numbers, or integers. the double data type I know is used for decimal calcualtions again. There are several variations of the double data type, such as long double, short double, long long double, etc. These are used for calculations concerning certain number ranges, whether or not you need them to be high, low, or negative numbers.