In 4GL, you use a key activation operation to control what happens when the application user presses a specific key on the keyboard. The operation is specified not for a particular function or control key, but for an FRS command, which is then mapped to a function or control key. 4GL provides the inquire_forms statement to retrieve information at runtime from FRS on the key that caused the activation. It also provides the set_forms statement to set various features of FRS dynamically.

4GL statements can activate 3GL or host language procedures that include embedded SQL statements and embedded forms statements.

4GL lets you assign a null value to a nullable variable through FRS.