Today computer plays an important role in almost every sector of our society because of its high capability. Although, computer has been used in education for more than 30 years, its function as a teaching tool is still relatively new and more development in this area is needed. Therefore, the objective of this research is to develop an authoring system for a teacher to create his own courseware. It is a general-purpose system, but primarily aimed at creating courseware in elementary caluculus. The authoring system developed is called SAS (Simple Authoring System). It is powerful, but easy to use. Users dont need to memorize any command because it will be displayed in the pull-down menu and pop-up menu. The system also provides facilities for drawing pictures, creating fonts and mathematical symbols. Various kinds of graphs can be constructed with area under them calculated. Stuents performance can be assessed and password can be used to protect the system from unauthorized users. SAS is very flexible, therefore teachers can create lessons to suit students of different backgrounds. A sequence of lessons can be programmed with SAL (Simple Authoring language), a special type of high-levl language developed for the SAS. Furthermore, the system may be used to creat courseware in other branches of mathematics or even other subjects. This research may also serve as the foundation for developing other authoring system in the future.