ISRO | ISRO CS 2015 | Question 51

In CRC if the data unit is 100111001 and the divisor is 1011 then what is dividend at the receiver?
(A) 100111001101
(B) 100111001011
(C) 100111001
(D) 100111001110


Answer: (B)

Explanation:

Step-1: 
Append (number of bits in divisor - 1) number
of zeroes at the end of data unit
Data unit = 100111001, append 3 zeroes at the end.
          = 100111001000

Step 2
Divide using xor subtraction:      
      ______________
 1011) 100111001000 ( 101000001
       1011
       ------
        01011
         1011
        -------
              01000
               1011
             --------
               011
             --------
Step 3
Perform Xor-sum of the remainder with the appended
zeroes in data unit.
= 100111001(000) xor (011)
= 100111001011

So, option (B) is correct.

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