The background and operation of charge transfer devices is reviewed, and a computer model simulation of focal plane arrays is presented. The model provides an option to predict the performance of a focal plane. With this program, any of the allowed materials, detectors, readout structures, or preamplifiers that make up a focal plane, may be selected to create new designs for analysis. Only surface channel devices are considered, and only references to the spectral dependence are presented. The computer model's operation and validity is supported by over 70 equations and more than 50 figures, including actual computer screen printouts. Standard equations followed by brief discussions are used to support the menu driven program. The structure and operation of the computer model is presented, but not the actual software source code.