A user friendly preprocessor was developed and documented for the plane and space frame and space truss structural analysis programs that are based on the matrix displacements method. This preprocessor is comprised of three programs. The main program in the preprocessor is to allow the user to create error free input data files. This program also allows modifications of existing input data files. The two other programs are the library manager and the graphics presentation. The library manager is used to manage the libraries of the element and material properties. The graphics presentation is used to display a plane structure on the graphics display. In Chapter 2, the development of a user friendly preprocessor is discussed. After a short review of the extension of the analysis program from plane frame to space frame in Chapter 3, the preprocessor and its supporting programs are described in detail in the user manual in Chapter 4. Possible extensions to the preprocessor are discussed in Chapter 5. The appendix contains examples of input data files for these structural analysis programs. / Master of Science