I am writing a programme which has a great demand for memory.
For example, I define a List
After some operation on "a", I want to delete "a", and release the memory it takes.
What is the command in Mathematica for memory release, just like "delete " in C++ ?
or in other words, I want to realize the following C++ code in Mathematica:
int * a;
a = new int;
delete  a;
I have tried the commands "Remove" and "Clear", it seems not the one I need.