HPlogo Interprocess Communication: Programmer's Guide: HP 3000 MPE/iX Computer Systems > Chapter 2 IPC Using Job Control Words and Other Variables

Special Considerations

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When your program uses both JCW and variable commands and intrinsics, there are some considerations you should keep in mind. Remember that a Job Control Word is a type of variable, but not all variables are JCWs. The variable commands and intrinsics operate on all entries in the variable table; they do not distinguish between JCWs and standard variables. On the other hand, JCW commands and intrinsics deal only with variable table entries that are flagged as JCWs.

Displaying JCWs and Variables

When you use PUTJCW or :SETJCW to set or alter a variable, that variable is "flagged" as a JCW. If you use the :SHOWJCW command, all JCWs set or last altered with PUTJCW or :SETJCW are shown.

When you create a new variable with HPCIPUTVAR or :SETVAR, that variable is not flagged as a JCW, even if it is within the valid range for a JCW. So if you use :SHOWJCW, that variable does not appear. Use the :SHOWVAR command, which displays both JCWs and standard variables.

It is possible to reset an existing JCW by using HPCIPUTVAR or :SETVAR. If you do so, and the new value is still within the valid range for a Job Control Word, then the JCW remains a JCW and you can display it with :SHOWJCW.

Warning Messages

If you use HPCIPUTVAR or :SETVAR to change a JCW to a value that is outside the valid JCW range, you see the following warning message:


   JCW VARIABLE RECLASSIFIED AS A STANDARD VARIABLE.

   (CIWARN 8126) 

This variable is no longer flagged as a JCW, and you must use :SHOWVAR to see it. FINDJCW will no longer return it; use HPCIGETVAR instead.

Likewise, you can use PUTJCW or :SETJCW to change a variable that was originally set using HPCIPUTVAR or :SETVAR. If the variable is within the valid range of JCW values, it becomes a JCW, and you see the following warning message:


   STANDARD VARIABLE RECLASSIFIED AS A JCW VARIABLE.

   (CIWARN 8127)

You can display this variable using either :SHOWVAR or :SHOWJCW.

Note that the value passed with the variable name is assigned to the variable; the command or intrinsic did its job. However, the variable is now classified differently.

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