Source : Free On-Line Dictionary of Computing

dot notation
     
         {Berkeley Unix} notation for an {Internet
        address}, consisting of one to four numbers (a "dotted quad")
        in {hexadecimal} (leading 0x), {octal} (leading 0), or
        (usually) decimal.  It represents a 32-bit address.  Each
        leading number represents eight bits of the address (high byte
        first) and the last number represents the rest.  E.g. address
        0x25.32.0xab represents 0x252000ab.  By far the most common
        form is four decimal numbers, e.g. 146.169.22.42.
     
        Many programs accept an address in dot notation in place of a
        {hostname}.
     
        (2000-08-10)