ILE C/C++ Programmer's Guide
A display file is used to define the format of the information
that you wish to present on a display. It is also defines how that
information is processed by the system on its way to and from the
display.
A subfile is a display file that contains a group of records with
the same record format that can be accessed by relative record number.
The records of a subfile can be displayed on a display station. The
system sends the entire group of records to the display in a single operation
and receives the group from the display in another operation. The
object type for both is *FILE.
To work with externally described display files use one of the
following:
- DDS through the Code/400 editor or the SEU.
- Screen Design Aid (SDA) or DSU What-You-See-Is-What-You-Get (WYSIWYG)
tools.
- An ILE C/C++ program can process display files as program described files
or as externally described files:
- For program-described display files, specify all formatting and control
information in the ILE C/C++ program that uses the file. To create a
program-described display file, specify SRCFILE(*NONE) on the CRTDSPF
command.
- For externally described display files, specify all formatting and control
information using DDS to describe the layout of the display. To create
an externally described display file, specify the name of the member that
contains the DDS source on the SRCFILE parameter of the CRTDSPF
command.
- If you are using a user-defined data stream (UDDS), hexadecimal 3F
(X'3F') blanks the display until the next display attribute.
If any CCSID conversion takes place and a character cannot be mapped to the
corresponding character in another code page, the character is mapped to
hexadecimal 3F. This will blank the screen until the next display
attribute. See Chapter 31, Internationalizing a Program for information on CCSIDs.
- The concept of clearing a file or opening a file using append mode does
not apply to display files.
- The input typedef for record format subfiles will contain fields with the
usage of I, O, B, and H. Input typedef for control record format
subfiles will contain fields with the usage of I, B, and H.
- To use a subfile, you initialize it, for example, by reading records from
a database file and writing them to a subfile. You must write them
using _Rwrited.
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