You cannot. Otherwise anyone can alter the data of whatever other running applications. Imagine what can I do by lurking your memory seeking for credit card numbers, and so on...
A pointer points to an address whose value is valid only inside the process that actually allocated it.
Another process (no matter if is identical or not to the first) see a different address map, and may even have pointers to a same address effectively pointing to completely different variables.
You can use "shared memory" between two processes, but it will be represented by different pointers.
To deal with this stuff you have to work with
Interprocess communication[
^]
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