Michael Fredman and Dan Willard created it in 1990 to simulate programming languages like C.[1] The word RAM model is an abstract machine similar to a random-access machine, but with finite memory and word-length.
It works with words of size up to w bits, meaning it can store integers up to
[2] The model allows both arithmetic operations and bitwise operations including logical shifts to be done in constant time (the precise instruction set assumed by an algorithm or proof using the model may vary).
In the word RAM model, integer sorting can be done fairly efficiently.
Yijie Han and Mikkel Thorup created a randomized algorithm to sort integers in expected time of (in Big O notation)
,[3] while Han also created a deterministic variant with running time
[5] Michael Fredman and Willard also solved the problem using fusion trees in
[6] Additional results in the word RAM model are listed in the article on range searching.
Lower bounds applicable to word RAM algorithms are often proved in the cell-probe model.