Stack architecture

Stack architecture: Instructions and operands are implicitly taken from the stack. A stack cannot be accessed randomly.

Stack machines use one- and zero- operand instructions. All instructions implicitly operate on elements at the top of the stack.

• Push X and Pop X instructions require a single memory address operand.
• Binary instructions (such as Add, Mult) use the top two items in the stack.

When working with stack architectures, arithmetic expressions should be structured with postfix notation ($Z=XY+$ as opposed to infix notation, $Z=X+Y$).

Parentheses are not needed to find order of operations, $Z=(X\cdot Y)+(W\cdot U)$ can be represented as $Z=XY\cdot WU\cdot +$ in postfix notation, and could generate instructions such as:

Push X
Push Y
Mult
Push W
Push U
Mult
Add
Pop Z

The result of each binary operation is stored at the top of the stack.