The HIDDEN directive allows you to hide specific data items from end users, while providing normal access to other data items. When you place this directive immediately before a data item in an FD, that item is hidden from end users. Field names affected by the HIDDEN directive are literally not placed into the system catalog. The user can neither read, modify, nor even know that this field exists.
The HIDDEN directive applies to only the elementary data item it precedes. Subsequent data items revert to normal read access. Note that you cannot apply the HIDDEN directive to group items and you cannot hide the key.
If you use the INSERT command on a table that has hidden fields, spaces (hex value 20) are put into the hidden fields, whether they are numeric or alphanumeric.
*(( XFD HIDDEN ))
In the following FD, "fee" is hidden from users in the resulting table.
FILE SECTION. FD jr-file. $XFD COMMENT This sample file demonstrates directives. 01 jr-record. 03 animal-info. 05 patient-id pic x(5). 05 atype pic x. 05 ctype redefines atype pic x. 05 dtype redefines atype pic x. 05 otype redefines atype pic x. 03 owner-info. 05 phone pic x(8). 05 owner pic x(30). 03 financial. 05 acct_no. 10 year pic x(2). 10 seq_no pic x(4). $XFD DATE=YYYYMMDD, USE GROUP 05 last_visit. 10 yyyy pic 9(4). 10 mm pic 9(2). 10 dd pic 9(2). $XFD HIDDEN 05 fee pic s9(5)v99. $XFD DATE=YYYYMMDD 05 date_paid pic 9(8).
Note that in the resulting table, the "fee" column no longer appears:
This directive is useful for hiding data like passwords, telephone numbers, and financial information — whatever information you don't want users to see.
You cannot include a HIDDEN field in a WHEN directive with a TABLENAME clause, because of the complexities of editing or adding records. In this situation, you must add the data, but since the field is hidden, you cannot see it and could add a value that would cause unexpected results.