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Using Externally Described WORKSTN Files
In addition to the field descriptions (such as field names and attributes), the DDS
for a display-device file are used to:
Format the placement of the record on the screen by specifying the line-
number and position-number entries for each field and constant.
Specify attention functions such as underlining and highlighting fields, reverse
image, or a blinking cursor.
Specify validity checking for data entered at the display work station. Validity-
checking functions include detecting fields where data is required, detecting
mandatory fill fields, detecting incorrect data types, detecting data for a specific
range, checking data for a valid entry, and processing modules 10 or 11 check-
digit verification.
Control screen management functions, such as determining if fields are to be
erased, overlaid, or kept when new data is displayed.
Associate indicators 01 through 99 with command attention keys or command
function keys. If a function key is described as a command function key (CF),
both the response indicator and the data record (with any modifications entered
on the screen) are returned to the program. If a function key is described as a
command attention key (CA), the response indicator is returned to the program
but the data record remains unmodified. Therefore, input-only character fields
are blank and input-only numeric field are filled with zeros, unless these fields
have been initialized otherwise.
Assign an edit code (EDTCDE) or edit word (EDTWRD) keyword to a field to
specify how the field’s values are to be displayed.
Specify subfiles.
A display-device-record format contains three types of fields:
Input fields
. Input fields are passed from the device to the program when the
program reads a record. Input fields can be initialized with a default value. If
the default value is not changed, the default value is passed to the program.
Input fields that are not initialized are displayed as blanks into which the work-
station user can enter data.
Output fields
. Output fields are passed from the program to the device when
the program writes a record to a display. Output fields can be provided by the
program or by the record format in the device file.
Output/input (both) fields
. An output/input field is an output field that can be
changed. It becomes an input field if it is changed. Output/input fields are
passed from the program when the program writes a record to a display and
passed to the program when the program reads a record from the display.
Output/input fields are used when the user is to change or update the data that
is written to the display from the program.
If you specify the keyword INDARA in the DDS for a WORKSTN file, the RPG
program passes indicators to the WORKSTN file in a separate indicator area, and
not in the input/output buffer.
For a detailed description of an externally-described display-device file and for a list
of valid DDS keywords, see the
DDS Reference
.
Figure 165 on page 333 shows an example of the DDS for a display-device file.
332 ILE RPG for AS/400 Programmer's Guide