What is the adverse effect of memory leak on the system?

Question

I know why memory leak happens but I don't know its harmful effects so please help

Answer 1

On any modern OS, it will not harm anything as the OS controls all of the physical memory, only exposing virtual memory to your application (assuming user mode, not drivers).
The only negative effect under normal conditions is that you will be hogging extra memory until your program exits, at which point the OS frees the memory you were using, leaked or not