Why do I have to use free on a pointer but not a normal declaration?

Question

Why do I have to use free() when I declare a pointer such as:

int *temp = (int*)malloc(sizeof(int))
*temp = 3;

but not when I do:

int temp = 3;

Answer 1

Normal declarations are put on the stack. When the function returns the stack pointer reverts to the value it had before the function was called, so the memory is automatically reclaimed.

Malloc-based declarations are allocated from the 'heap', which requires the programmer to manage allocations and deallocations.