Abstract: Users are not concerned with the computer faults but they need the computer working in a correct mode. Specially, in critical circumstances. Fault Computing (FC) plays a important role, especially, since, early 50’s. This area opens a wide aspect to be researched area, this study involves varieties of categorizations of techniques towards the effort to make system fault tolerant, modeling and testing helping with system development and bench-marking to evaluate and compare systems. The concept, modeling and methodology of fault tolerant computing are very much controversial to software while they are considered fairly mature for hardware. Often refer to real-time critical system embedded systems. Faculty tolerant computing far from strictly application the system development and operational process in the above area.