Question

Certain CPU uses expanding opcode. it has 32 bit instructions with 8 bit Addresses. It supports One Address and Two Address instructions only. If there are two Address instructions: the maximum number of one Address instructions is:

• A. $(2^{24}-n)\times 2^8$
• B. $(2^{16}-n)\times 2^{16}$
• C. $(2^8-n)\times 2^8$
• D. $(2^{16}-n)\times 2^8$

Answer 1

The correct option is D $(2^{16}-n)\times 2^8$

option (c)

$\text{max number of 2 Address instruction is}{2}^{16}$



$\text{But is uses 'n' only : so, remaining free combinations}(2^{16}-n)\text{are left for one Address instructions.}$

$\therefore \text{Max number of one Address instruction to be formualted:}$

$(2^{16}-n)\times 2^8$