hexadecimal is used, because the conversion is almost free (as oposed to decimal) Also, phone numbers (for last 50 years or so) actually are hexadecimal string

hexadecimal is used, because the conversion is almost free (as oposed to decimal) Also, phone numbers (for last 50 years or so) actually are hexadecimal strings (with extra characters - denoted ABCD*# - reserved for various special purposes).