Topic       : TOS - das Betriebssystem
Author      : 
Version     : tos.hyp (5. März 2013)
Subject     : Programmieren/Atari
Nodes       : 3001
Index Size  : 93602
HCP-Version : 5
Compiled on : Atari
@charset    : atarist
@lang       : 
@default    : Titel
@help       : 
@options    : +g -i -s +x +zz -t4
@width      : 70
View Ref-File15.13.2.1  XAcc message groups                                     TOS

[Note: The "levels" used in previous XAcc versions have been replaced 
by this new concept. Compatibility issues are discussed in a special 
section at the end of this document.]

Both main applications and accessories can have widely different needs 
for communication with other programs. Therefore XAcc defines several 
groups of related messages that deal with a certain range of data 
types. The message groups always indicate the messages understood by a 
program, not the messages it might send to other ones. If a program 
supports a certain message group, it must correctly respond to all 
corresponding messages, whether it can actually use the supplied data 
or not.

In addition to message groups, there are the so-called "basic 
messages", which must be supported by any XAcc-aware program, and 
program-specific so-called "special messages".

The basic messages deal solely with identification, but no real data 
exchange. They are already sufficient for programs that either do not 
exchange data with others at all or use only special messages to 
communicate with a number of other specific programs.

 Message group 1 specifies the exchange of ASCII-format character 
                 data.

 Message group 2 deals with the exchange of drawings and pictures 
                 using the GEM metafile format and the GEM bit-image 
                 file format.

Future extensions might include sound or spreadsheet data. In 
addition, a message group could be defined to handle command 
interchange between applications, e.g. for a "drag&drop" protocol.