Chapter 18 – Using Dynamic 
Memory Allocation

1. malloc() allocates requested memory on the heap, as does calloc(). However, calloc() initializes the allocated memory to zero before returning.
2. The lifetime of memory allocated on the heap begins when the memory is allocated and ends either when free() deallocates that memory or when the program ends.
3. A memory leak occurs when a block of memory is no longer referenced via its pointer and the block has not been deallocated. It is unretrievable until the program exits.
4. There are several important reasons to create test code:
   1. You prove the validity and correctness of your code.
   2. As the code changes, you can verify that the code still works as intended.
   3. Confidence in modifying code that has tests is higher.
   4. Tested code tends to require much less reworking and debugging.