When customising Chris21 you will usually make changes to the Data Dictionary (DMA) and the Field Definitions (FLD) forms. DMA is for changes to the structure of a file while FLD lets you customise the way the form looks in Chris21. See my blogs Customising Chris21 the Right Way and Customising Chris21 Forms – How to Place a Field onto a Form for more information.
I want to bring your attention to the Field field on FLD. If you are customising Chris21 and want to add a new field you must take care when choosing the Field number.
You will find that you can enter any number you choose into this field. Therefore it may seem like an arbitrary number that is of little significance. The most important point is to ensure that you do not enter a duplicate Field number.
When you look at the list of Field numbers in the screenshot above, you will notice that there are no duplicates. Ideally you will create new fields in ascending Field number but this is not critical. But what is critical is that you don’t use a number that has already been used. Unfortunately, Chris21 will let you use a duplicate number without flagging an error. So you could do this by mistake without noticing.
What is the problem with using duplicate Field numbers?
When you use a duplicate Field number Chris21 will only display one of the fields on your form. Therefore, even though you may have correctly placed your new field at a different position on your form, the original field will no longer be displayed.
The easiest way to avoid this is to identify the highest field number that has been used on the form you are customising. You can do this by searching for the Form Identifier on FLD as shown in the screenshot above. Then simply use the next available number.
Keep this tip in mind when customising Chris21 so that you will not mistakenly remove fields from displaying on your forms.