When using SDA to design screens, there are times when you need to change the usage of a field that is already defined. If you read the help screen for "Design Image Work Screen," it will explain how to add a field with a given usage (input, output or both), how to copy a field and how to delete a field. It does not explain how to change the usage of an existing field. This seems to imply that you cannot do it, and you may end up deleting the field and re- creating it with a different usage.

There is a much easier way. To change the usage of a field already defined, type the appropriate field usage character over the first usage character already displayed on the screen and press Enter. Character fields can be changed to I (input), O (output) or B (both). Numeric fields can be changed to 3 (input), 6 (output) or 9 (both). You cannot change a field from numeric to character or vice versa. This technique works for both user-defined fields and fields referenced from a database.

For example, if you have a customer name field on the screen which is defined as B (both), you can change it to output only by replacing the first B with an O and pressing Enter. SDA changes the string of Bs into a string of Os.