DSDR KB:

The following is a link to a quick reference for data types in Stata:

http://www.stata.com/help.cgi?datatypes

Variables can contain numbers or strings. Numeric variables can be stored as integers (bytes, integers, or longs) or floating point (float or double). These types differ in the range of precision of the values they can hold. Stata encourages you to record your data as efficiently as possible, so if you have dummy variables (0,1) it makes sense to define them as bytes as this takes the least amount of space in memory.

String variables can have varying lengths up to 244 characters (str#). The length of the string is indicated by the # key, str6 vs str20.