A half byte is known is?
A half byte is known is Nibble.
A group of four bits, or half a byte, is sometimes called a nibble or nybble. This unit is most often used in the context of hexadecimal number representations, since a nibble has the same amount of information as one hexadecimal digit.
In computers and digital technology, a nibble (pronounced NIHB-uhl; sometimes spelled nybble) is four binary digits or half of an eight-bit byte. A nibble can be conveniently represented by one hexadecimal digit. ... A signal may be encoded in quadbits rather than one bit at a time.