This section describes the specifications for a field user validation function that you write to install in a field. System validation functions for a field do not have the same specifications. If you want to replace one of the system validation functions, see Chapter 36, "Adding New Field Types and Picture Control Characters."
Field validation functions must be integer functions that return FALSE if the field entry is invalid and return TRUE if the field entry is valid.
Validation Functions for Data Fields
Validation Functions for Memo and Tickertape Memo Fields
What You Should Not Do in Field Validation Functions
