How to use and modify a public member data which was declared in another fix command class by using pointers?

Please keep the list in the loop.

This is a basic C++ issue. You've added an array
to a specific fix class of your own. You can't access
it thru a generic fix pointer, since Fix.h doesn't know about
it. Your have to cast the generic pointer to one to your class.
Something like:

double **efg = (FixABCD * fix[i])->efg;


Please keep the list in the loop.

FYI, with most e-mail programs, you need to click on
"Reply to all" instead of "Reply" to make sure that a
copy is sent to the list. otherwise you can add
the email address of the list in the cc: field.

this way the entire conversation is archived in
the mailing list archives and somebody that has
similar problems as you can research them in
the archives and thus everybody benefits.