C language only accepts two data types namely primary data types and derived data types. The primary data types will come in the form of integer, character, void, and floating point. Derived data types come in the form of an array of union, structure, and the last is the pointer.
The data type is important because this will help determine if the data that is placed will be able to hold. For example, variable y has already been declared as float, this will only show data related to the floating point of the variable. If variable y will be declared as an integer then only data related to integers will appear.