To describe a power system network (circuit) for simulation and analysis, both load flow and transient stability programs require that the system network information be mapped into data files. Traditionally, this mapping procedure is usually done by hand-coding, line by line. For some analysis programs such as the BPA Load Flow and Transient Stability Programs, data entry is strict--requiring data to be placed in individual columns. This mapping procedure is tedious, time-consuming and prone to error. Obviously, a graphical interface for both load flow and transient stability programs would be a much more efficient means for data entry and result visualization. Using a graphical interface, power system engineers do not need to hand-code the input data files as previously required. Instead, now, they are able to define the power system network by using an one-line diagram and the computer takes care of the rest of the work of data mapping from the one-line diagram into data files. Also, the visualization of simulation results provides an easy way for output analysis and the BPA Package Manager program developed here gives users more freedom from typing and remembering various commands and data file names in each procedure. In addition, it is important to note that the methods used in this thesis could be a plied in other load flow and transient stability simulation programs or even other fields of power system industry easily. (Abstract shortened by UMI.)