Electronics and Communication Engineering - Digital Electronics - Discussion

22. 

The greatest negative number which can be stored is 8 bit computer using 2's complement arithmetic is

[A]. - 256
[B]. - 128
[C]. - 255
[D]. - 127

Answer: Option B

Explanation:

The largest negative number is 1000 0000 = -128.


Geetha Adainjan said: (Jul 1, 2015)  
Why 1111 1111= -255 not came here? Please clarify it.

Pratik said: (Jul 29, 2015)  
It is not largest number.

Rekha.V said: (Aug 21, 2015)  
The greatest negative number which you can represent using N bit (of course signed) could be -2^(N-1).

So for 8 bit 2^7 = -128.

Rekha.V said: (Aug 21, 2015)  
The greatest negative number which you can represent using N bit (of course signed) could be -2^(N-1).

So for 8 bit 2^7 = -128.

Sudipta Majumder said: (Sep 16, 2015)  
Greatest positive number = 01111111.

Taking 2's complement to get greatest negative number that is = 10000001.

Now put the formula and we get = -127.

Sunanda said: (Mar 19, 2017)  
Greatest positive number is 255, right?

Sandy said: (Mar 24, 2017)  
No, the largest positive no is 127.

132,64,32,16,8,4,2,1.
0 1 1 1 1 1 1 1.

Shubham said: (Aug 12, 2017)  
For 2's compliment.

The range is -(2^n-1) to +((2^n-1)-1) and this is different in the case of 1's and signed representation.

Divyesh Makwana said: (Feb 27, 2018)  
The largest Negative number in 8 bit is 01111111 and 2's complement of it in 10000000 which is -127.

Pavan said: (Jun 25, 2018)  
In 8bit, 11111111 is the largest right?

Pavan said: (Jun 25, 2018)  
And why 0111111 is largest? please explain.

Dhanya said: (Jul 30, 2018)  
For 2's compliment representation, Range is {-2^(n-1) ) to +(2^(n -1))-1}.
Here n=8 ,then { (-2^(8-1)) to +(2^(8-1))-1}.
-2^7 to +(2^7)-1.
-128 to +127.

So, the greatest negative number in 2'compliment representation is - 128.

Dhanya said: (Jul 30, 2018)  
-128 in 2's compliment form = 2's compliment of + 128.
+128 in binary form=01111111.
2's compliment of 01111111=10000001.

Sumesh said: (Jul 30, 2018)  
+128 = 10000000,
-128 =2's compliment of 10000000,
=1's compliment of 10000000 +1,
= 01111111 +1,
=1000000.

Tshering Dorji said: (Jan 1, 2021)  
Then, what is the way to find the largest negative and positive number for 1s complement and signed number?

Please, anyone, tell me.

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