All integer types are accepted by the preprocessor. Even though some integer types have Pascal constraints, such as the subranges and enumerations, EQUEL does not check these constraints, either during preprocessing or at runtime.

The type boolean is handled as a special type of integer. EQUEL treats the boolean type as an enumerated type and generates the correct code in order to use this type to interact with an Ingres integer. Enumerated types are described in more detail later.