A flag column holds a yes-or-no value. Its name ends in `_flag`, such as `create_flag`, and it stores a single character: `Y` for yes and `N` for no. Screens show it as a check box. The postfix and the two values are settings of the application: "Postfix for Flag Field", 'Flag Field Value for "yes"' and 'Flag Field Value for "no"'. The business layer refuses any other value in a flag column.