In the 4B/5B encoding scheme, every 4 bits of data are encoded in a 5-bit codeword. It is required that the codewords have at most 1 leading and at most 1 trailing zero. How many such codewords are possible?
(A) 14
(B) 16
(C) 18
(D) 20
Answer: (C)
Explanation: The possible codewords should not have 00xxx or xxx00
=> Total possible combinations of 5 bits – for (00xxx or xxx00)+ (00×00) {as 00×00 is subtracted twice once each from both cases}
=> 32 – (8+8) +2 = 18
Quiz of this Question