RE: What's the difference?

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Omitted parms in the middle.

In OPM this was done by checking, not PARMS, but the address of each
field.  For example, if I called a program using parm1 and parm4 but not
parm2 nor parm3.  The called program would check the address of parm2 by
using if %addr(parm2)=*null.  If it was null do not do anything with it.
Do not even try to clear it, move blanks or zeros to it, not anything.
Otherwise you get the MCH error.

When would this ever happen in real life?  When using a command to drive
your program.  For example I made a command called RTVJOBD.  This command
calls a rpg program.  Now, the program using this command may not care
about some obscure job description property, thus it won't put a variable
name in that parameter.  If the parameter is not null then I assign the
value of that variable from a result field from the api to retrieve a job
descriptions attributes.

Rob Berendt
--
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."
Benjamin Franklin