Host Software Compatibility - IBM 3270 G Manual

Host Software Compatibility
Under GDDM Release 4, most existing 3270 alphanumeric and graphics
programs (including those written for GDDM Release 3 or earlier) can be
used at the work station without modification, provided that any required
hardware functions are available on the work station. If you intend
running programs that have been written for the 3278, 3279, or 3277GA, you
should be aware of the following incompatibilities:
• Graphics are displayed at the work stations using all-points-addressable
screens. Support for programmed symbols is therefore limited to two
single-plane sets. Existing programs that use programmed symbol sets
directly (not through GDDM) to create graphics may therefore need to
be rewritten.
• User-defined character sets or fill patterns for GDDM application
programs may need modification to suit the cell size of the new displays.
• The maximum size for a picture segment that is to be transferred
between host and work stations is 63 K bytes. If you want to transfer a
segment that is larger than 63 K bytes, GDDM will automatically split
it into manageable segments and transfer them in unretained mode,
thus precluding interactivity.
• The work stations do not support the attachment of 3270 magnetic
devices or of a selector pen. However, the Cursor Select key on the
work station keyboard provides an input function equivalent to that of
the selector pen.
• Application programs for the 3277GA that have been written to use
GDDM need only minor modifications to run on a work station that has
a 5379 Display with the dual-screen feature.
• The Graphics Control Program does not support the data stream that is
used by the 3277GA. Application programs that generate their own data
stream for the 3277GA thus require major modifications before use with
the Graphics Control Program.
For limitations on running 3270 programs with the work stations, refer to
Appendix B.
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Introducing the IBM 3270 Personal Computer/G and /GX Work Stations