In C variables have to be of a specific data type. Luckily, C defines only 5 basic data types that it works with, so it’s not too difficult to choose what you want. All the data types are covered in this article, including their size modifiers unsigned, signed, short and long.
With variables, data types, flow control, functions, expressions, statements, subroutines, and such under your belt, you are prepared to understand more fully just about any programming that comes your way from any of the popular general purpose languages out there. That’s really the core of what makes up programming today (granted you’re not using a more specialized language such as Prolog or LISP).