How to determine RTE-A revision
         ========================================
 
At 6.0, the variable $DATC was added to make it easy to determine
the revision, this won't help you if you are pre 6.0.
 
Simply echo $DATC (or use the CI "set" command to list all variables)
 
For pre 6.0 systems, you can just run LINK, it's revision will be
very close to the OS.
 
===========================
Other revision information:
===========================
 
$OPSY is a system entry point whose value typically changes with
each major OS/revision.
 
The following table lists the possible values of $OPSY and
the corresponding system type and revision:
 
       -7  =  RTE-MI
      -15  =  RTE-MII
       -5  =  RTE-MIII
       -3  =  RTE-II
       -1  =  RTE-III
       -9  =  RTE-IV,RTE-IVB
      -17  =  RTE-6/VM
      -13  =  RTE-4E
      -29  =  RTE-XL
      -31  =  RTE-L
      -37  =  RTE-A Pre-Rev 2440
      -45  =  RTE-A.1
      -53  =  RTE-A Rev 2440, 2540, 4010
      -61  =  RTE-A Rev 5000 through 5270
     -125  =  RTE-A Rev 6000 and 6100, and later
 
$OPSY is variable that can be echoed from CI, or can be determined
programmatically as follows:
 
     FTN7X
     $ALIAS IOPSY = '.OPSY', DIRECT
           PROGRAM FINDOPSY
           INTEGER OPSYS_ID
           OPSYS_ID=IOPSY()
           WRITE(1,*)OPSYS_ID
           END
 
=================================
CI "REVLEVEL" versus RTE revision
=================================
 
The CI command "REVLEVEL" will give you the revision level of CI. The
following table shows CI REVLEVEL's and the corresponding Operating
System revision. Note that this is for a system with the CDS version of CI.
 
     CI REVLEVEL       OS Revision
     ------------------------------------
     <850109.1743>        2440
          :                 :
     <851022.1015>        2540 (4.0) or 4010
     <870305.1535>        5000
     <881004.1257>        5010
     <900306.1214>        5020 or 5240
     <911121.1717>        5270
     <921124.1404>        6000
     <930804.1632>        6100
     <950206.0858>        6200 or 6210      Current
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