Typedef can be used to define default column characteristics, which is helpful when standardization of the characteristics for a number of columns at the same time is wanted. Then, when the typedef is selected as the base type in the General Column property page, the column will inherit all of the typedef's attributes. The information includes:
Defining general attributes such as the type, length, and precision.
Defining TAOS form input attributes such as the input mask.
Defining output attributes the background and output masks.