Assemble a stack

I thought it might be helpful to explain the stack instructions a bit more in detail. The stack instructions involve the following components:

• a memory area
• a base pointer
• an index value
• a PUSH instruction
• a POP instruction
• a value to push (or pop)

The base pointer (BP) contains the address of some memory cell. The index register (IX) contains the index of the element in the stack. Written together as BP[IX] there refer to the address of a specific element in the stack. The address is the sum of BP and IX. Note that so far we could also write IX[BP] and it would still refer to the same address. The difference starts when using the PUSH/POP instructions, which we will look at next time.

Here is an example for values of BP and IX pointing to some area of memory with unknown content.

            BP: 0x0039
            IX: 0x0000

            0x38: ?
BP[IX] ---> 0x39: ?
            0x3A: ?
            0x3B: ?