The words 'computer' and 'computing' are both vague and very broad. Even some of those involved in the field of artificial intelligence believe that (some?) molecules are computers. Or, more precisely, they argue that molecules are “closed physical systems” which compute. That is, molecules carry out information processing. Or, alternatively, they receive input, work on that input, and then produce/deliver output.
State Register = RNA
States = Amino acid
Instruction Table = DNA codon table
Output Tape = Proteins
“... the window in front of me is a very simple computer. Window open = 1, window closed = 0. That is, if we accept Turing’s definition according to which anything to which you can assign a 0 and a 1 is a computer, then the window is a simple and trivial computer.” (1997)
Modelling Physical Systems
Putnam, Hilary. (1991) Representation and Reality
Rana, Fazale. (2012) 'Biochemical Turing Machines “Reboot” the Watchmaker Argument'
Searle, John. (1992) The Rediccovery of Mind (pages 2008/9).
-- (1997) The Mystery of Consciousness