A simple byte oriented microcontroller has a 16-bit stack pointer (SP) register that points to the next empty memory location in the stack. A PUSH instruction loads an operand into the stack and then decrements the SP; a PULL instruction increments the SP and then unloads an operand from the stack. Based on the above description, which of the following statements about the stack is true?? 1. This stack structure will not work since the stack pointer is sometimes incremented and sometimes decremented.
2. The stack will always fill up toward higher memory addresses.
3. The stack will fill up toward either lower memory or higher memory addresses depending on the number of items stored.
4. The stack will always fill up toward lower memory addresses.