Question

A computer supports 16-bits instruction with each address of 6-bits, If there are maximum 128 1-address instruction then the number of 2-address instruction are supported in the computer system is _____________.

• A. 14
• B. 13
• C. 15
• D. 12

Answer 1

The correct option is A 14

option (c)

Suppose n 2-address instruction are supported.
2-address instruction format.
$\text{max opcode}=2^4=16$
$\underset{–}{\text{used opcode}=n}$
unused opcode = 16 - n

1 -address instruction format
$\text{max 1-address instructions :}(16-n)\times 2^6=128$
$\therefore$ n = 14