Expend opcode.

Question

in a computer instruction format, the instruction length is 11 bits and the size of an address field is 4 bits. The computer support:

 2-address instructions

 1-address instructions

 0-address instructions

All three type of instruction must be exist in the computer (i.e. there is at least one instruction from each type)

How many maximum number of instruction supported by this computer?_

Answer 1

For max no of instructions, we need max instructions of 0-address

Thus, one 2-address instruction, one 1-address instruction, others 0-address

So, total 2-address inst = 1* 2^8 = 256
Total 1-address inst = 1*2^4 = 16
So, 0-address instructions = 2^11 - 256 - 16 = 2048 - 256 - 16 = 1776

Thus, total inst = 1776 + 1 + 1 = 1778

Comments

Thankyou bro but please just see this ques i already solve like is it correct?

consider the machine in which instructions are 12 bits in length and addresses are 4 bits in length. There are 3 classes of instructions: Class A: 2 addresses Class B: 1 address Class C: 0 addresses All three type of instruction must be exist in the computer (i.e. there is at least one instruction from each type)
What is the maximum total number of instruction possible in machine?____
Here total 2^12-2*2^8-1*2^4=3568
right
then
3568+ 2+ 1 = 3571 is it correct ???  
 

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Why are you considering 2 instructions of 2-address class? Just consider one!

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But why answer is 3826 (maximum) how it is psbl ?

I'm taking 2 bec it is given or what should i do for max please tell me bro i'm confused

and what shold we do for minimun like the min is 46 i'm not getting that.

 

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For max no of instructions, we need max instructions of 0-address. As they have said atleast 1 instruction of each type, we need to take 1 instruction of 1-address and 2-address.

This, 1 inst of 1-address, 1 inst of 2-address and others of 0-address.

Thus, one 1-address inst and one 2-address inst = 1*2^8-1*2^4
Remaining inst (for 0-address) = 2^12-1*2^8-1*2^4 = 3824

Thus, total instuctions (ie. opcodes) = 3824 + 1 + 1 = 3826

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OOO understood bro
bhoot bhoot Dhnyavaad dost....
But  2^12-2*2^8-1*2^4 = 3568 not 3824 bro

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Welcome! :)

Also thanks for pointing out my mistake....I have corrected it now