The following calls are already in use in various systems
and/or in DOS+, CPM 2/3, MPM, CPM86.

  0 ..  60   CPM2/3, ZRDOS (some holes, but do not use)
 61 ..  83   BYERSX  (for CPM2 or DOS+) (also BYE338, BYE508)
 84 ..  85   BYE508 and BYERSX conflict
 86          BYERSX
 87          BYERSX master control call (for CPM2 or DOS+)
 88 ..  93   BYERSX  (for CPM2 or DOS+)
 94 ..  95   reserved for RSX extensions 
 96          ENSPOOL (for CPM2 or DOS+)
 97          UNSPOOL (for CPM2 or DOS+)
 98 .. 103   CPM3 MPM CPM86
104 .. 105   DOS+ CPM3 MPM CPM86
106 .. 112   CPM3 MPM CPM86
113 .. 114   reserved for RSX extensions
115          DSKDRIVE or CPM86 graphics system
116 .. 129   presently unused. Treat as reserved
130 .. 151   presently unused.  
152          CPM3
153 .. 199   presently unused.  This is the recommended general use block.
200 .. 248   reserved for DOS+
249          XJOB (for DOS+)
250 .. 254   reserved for supercalls (using b reg)
255          Used in HP125 extension systems
h