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
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View Ref-File15.13.2.2  Compatibility considerations                            TOS

There are two major changes with respect to the original XAcc 
definition:

  1. "Levels" have been replaced by "message groups"

     The motivation for this change was that the classification 
     according to exchangeable data types was not really a 
     hierarchical one; there is no reason why a programm accepting 
     graphics should also be able to understand text. The new scheme 
     makes no such arbitrary assumptions.

     There is only one situation in which a possible incompatibility 
     could occur: an application following the "old" convention 
     encounters a "new" application and one of them indicates 2 in the 
     level/message group byte. This would be interpretes as "graphics 
     only" by one and as "graphics and text" by the other. Since the 
     number of level-2 applications was always extremely small (in 
     fact, the author knows only of a single one), this should be no 
     problem in practice.

  2. Extended names have been introduced

     This could lead to a problem in the extremely unlikely case of an 
     "old" application using a name string which is accidentally 
     followed by "XDSC".

In any case it is expected that most applications will be converted to 
the new rules soon, if only to support MultiTOS.