The Free On-line Dictionary of Computing (30 December 2018):

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)