[jbangert]

This comes from a restriction of almost all existing computer architectures. You have a small amount (16 on amd64) of 'variables' called registers that you can directly work with. Additional variables have to be loaded from and stored in memory, which is slower and requires you to know that variables address (pointer) -- which is just an integer with special meaning. In C, variables you never take a pointer to might live exclusively in a register, and all local variables are stored at a fixed offset to a special 'stack pointer' which is kept in a dedicated register.

Some architectures try to have a more sophisticated approach and have some sort of 'fat pointer' in which pointer values have a special tag and are subject to special rules so they can only point to valid objects. The exact rules used and what constitutes 'valid' is specific to the architecture. Intel has introduced mpx on newer processors to check array bounds with such a scheme, and older processors such as LISP machines have much stronger (but less efficient) schemes.