Q. Evaluation Stack Architecture?

A stack is a data structure which implements Last-In-First-Out (LIFO) access policy. You can add an entry to the with a PUSH(value) as well as remove an entry from the stack with a POP( ). No explicit operands are there in ALU instructions however one in PUSH/POP. Illustrations of these computers are HP 3000/70, Burroughs B5500/6500 etc.

On a stack machine 'C = A + B'may be implemented as:

        PUSH A

        PUSH B

ADD         // operator POP operand(s) and PUSH yield(s) (implicit on top of stack)

POP C

Stack Architecture: Pros and Cons

• Small instructions (don't require many bits to specify the operation).
• Compiler is easy to write.
• Lots of memory accesses needed - everything that's not on stack is in memory. So the machine performance is poor.