Word RAM

In theoretical computer science, the word RAM (word random-access machine) model is a model of computation that is a random-access machine able to do bitwise operations on a single word of bits. The model was created by Michael Fredman and Dan Willard in 1990 to simulate programming languages like C.
Model.
The word RAM model is an abstract machine similar to a random-access machine, but with additional capabilities. It works with words of size up to bits, meaning it can store integers up to size formula_1. Because the model assumes that the word size matches the problem size, that is, for a problem of size , formula_2, the word RAM model is a transdichotomous model. The model allows bitwise operations such as arithmetic and logical shifts to be done in constant time. The number of possible values is , where formula_3.
Algorithms and data structures.
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) formula_4, while Han also created a deterministic variant with running time formula_5.
The dynamic predecessor problem is also commonly analyzed in the word RAM model, and was the original motivation for the model. Dan Willard used y-fast tries to solve this in formula_6 time. Michael Fredman and Willard also solved the problem using fusion trees in formula_7 time.