We give semantics for notions of computation, also called
computational effects, by means of operations and equations. We show
that these generate several of the monads of primary interest that
have been used to model computational effects, with the striking
omission of the continuations monad, demonstrating the latter to be of
a different character, as is computationally true. We focus on
semantics for global and local state, showing that taking operations
and equations as primitive yields a mathematical relationship that
reflects their computational relationship.
