Which bit patterns cannot be expressed in hexadecimal notation?

Question

Hello, I have a problem in understanding what this question means

Which of the following bit patterns cannot be expressed in hexadecimal notation?

A. 11111111 B. 1001 C. 110011 D. 100000000001

Answer 1

Like you, I'm puzzled by this one. I'd expect any bit pattern to be able to be expressed in Hex.

The usual process is to split the binary number into groups of 4 bits (a "nibble") and then convert to a hex digit.

While I believe each of these four binary numbers can be converted to hex, the odd one out is (C) which is the only one with binary digits not a multiple of 4. I think normally one would just assume that 110011 implied 00110011 (i.e. 8 binary digits with 2 leading zeros). But perhaps the question is indicating that, technically 6 digits only (rather than 4 or 8) can't be converted directly.

However, I think any binary to hex converter will treat 110011 and 00110011 as the same.

A. 11111111₂

= 1111 1111 (15, 15)

= FF₁₆

B. 1001₂

= 1001 (9)

= 9₁₆

C. 110011₂

= 11 0011 (3, 3)

= 0011 0011

=33₁₆

D. 100000000001₂

1000 0000 0001 (8, 0, 1)

= 801₁₆