model of computation for computer models simulating complex systems see computational model in computer science and more specifically in computability theory and computational complexity theory a model of computation is a model which describes how a set of outputs are computed given a set of inputs this model describes how units of computations memories and communications are organized the computational complexity of an algorithm can be measured given a model of computation using a model allows studying the performance of algorithms independently of the variations that are specific to particular implementations and specific technology models models of computation can be classified in three categories sequential models functional models and concurrent models sequential models include finite state machines pushdown automata turing machine functional models include lambda calculus recursive functions combinatory logic cellular automaton abstract rewriting systems concurrent models include kahn process networks petri nets synchronous data flow interaction nets uses in the field of runtime analysis of algorithms it is common to specify a computational model in terms of primitive operations allowed which have unit cost or simply unitcost operations a commonly used example is the random access machine which has unit cost for read and write access to all of its memory cells in this respect it differs from the abovementioned turing machine model in modeldriven engineering the model of computation explains how the behaviour of the whole system is the result of the behaviour of each of its components a key point which is often overlooked is that published lower bounds for problems are often given for a model of computation that is more restricted than the set of operations that one could use in practice and therefore there may be algorithms that are faster than what would navely be thought possible categories there are many models of computation differing in the set of admissible operations and their computations cost they fall into the following broad categories abstract machine and models equivalent to it eg lambda calculus is equivalent to the turing machine used in proofs of computability and upper bounds on computational complexity of algorithms and decision tree models used in proofs of lower bounds on computational complexity of algorithmic problems stack machine 0operand machine accumulator machine 1operand machine register machine 23 operand machine random access machine cellprobe model fernndez maribel 2009 models of computation an introduction to computability theory undergraduate topics in computer science springer isbn9781848824331 savage john e 1998 models of computation exploring the power of computing addisonwesley isbn9780201895391 this computer science article is a stub you can help wikipedia by expanding itvte 