How to Manage Memory

Space that needs to persist beyond the scope of a single subroutine is often called heap allocated. A chunk of memory is useless, hence garbage, when nothing refers to it. Depending on the system you use, you may have to explicitly deallocate memory yourself when it is about to become garbage. More often you may be able to use a system that provides a garbage collector. A garbage collector notices garbage and frees its space without any action required by the programmer. Garbage collection is wonderful: it lessens errors and increases code brevity and concision cheaply. Use it when you can.

The creation of new objects is moderately expensive on any system. Memory allocated directly in the local variables of a subroutine, however, is usually cheap because the policy for freeing it can be very simple. You should avoid unnecessary object creation.

Sometimes you have to explicitly free allocated space so it can be reallocated rather than rely on garbage collection. Then you must apply careful intelligence to each chunk of allocated memory and design a way for it to be deallocated at the appropriate time. The method may differ for each kind of object you create. You must make sure that every execution of a memory allocating operation is matched by a memory deallocating operation eventually. This is so difficult that programmers often simply implement a rudimentary form of garbage collection, such as reference counting, to do this for them.