Most programming languages require the programmer to declare the data type of every data object, and most database systems require the user to specify the type of each data field. The available data types vary from one programming language to another, and from one database application to another, but the following usually exist in one form or another:

Conetic's data type page
This is a page on data types from Conetic Software Systems' online reference manual, offering information on what data types do, descriptions of data types and formatting rules.