Primitive and build-in data types, char short int long float double - some even come in the two flavors signed and unsigned. Be aware that there is no boolean in c. You can use the sizeof() method to detect the size of any of those data types. Char for example has the size of 1 (one byte). Signed and unsigned is important for char, short, int long - every integer data type. While coding in C you have to be aware, that the size of int, long and long long depends on the system and may vary. Therefore it is highly recommended to use sizeof whenever possible. For floating point types there is float, double and long double. Check them out as well. Most of the integer types use %d for printf, most of the float types use %f. So if you haven't looked it up yet, printf %'s you should now are at least c,f and d.