Adding program to auto run after being ran

I need to know how to make a program add itself to auto-run after being ran.
Thanks in advance.

Have you tried creating a shortcut in the startup folder.
I'm not sure how to programmatically do it in C++ though.

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Trân Tr?ng

Well the thing I want to do with it is to make a harmless troll program that when someone downloads and runs it, it auto runs every time they start their PC