6809 BBC API          6809 FLEX                 6809 OS9

0000 +--------+     0000 +--------+
  DP | Direct |       DP | Direct |
     |  Page  |          |  Page  |
0100 +--------+     0100 +--------+            Arbitary     Arbitary
                         |        |            Address      Address
                         |  BASIC |        U  +--------+   +--------+
                         :  code  :       DP  | Direct |   |        |
                         |        |           |  Page  |   |  BASIC |
0400 +--------+    BasEnd+--------+    U+0100 +--------+   |  code  |
     | Work   |          | Work   |           | Work   |   :        :
     |  space |          |  space |           |  space |   +--------+
0800 +--------+          +--------+    U+0500 +--------+
PAGE |        |      PAGE|        |       PAGE|        |
     :        :          :        :           :        :
HIMEM| stack  |          |        |           |        |
8000 +--------+          :        |           :        |
     |  BASIC |          :        :           :        :
     :  code  :          | stack  |           | stack  |
     :        :     HIMEM+--------+      HIMEM+--------+