The course 18.013A as it appears here is intended as a one and a half term course in calculus for students who have studied calculus in high school. It is intended to be self contained, so that it is possible to follow it without any background in calculus, for the adventurous. It makes use of some tools that are relatively new, such as applets, which are intended to make the subject easier to learn and more fun. However it was not our intention to make this course merely an easy calculus course, covering all the same material as the traditional course, but easier to assimilate because of the applets and use of spreadsheets. Modern labor saving devices in practice do not make life easier and simpler. Instead they save us time that allows us to do more in our lives and to make life more complicated and busier than ever. In the same sense it is our hope that these new tools allow the student to learn more and learn more thoroughly with the same amount of, and even perhaps more, effort than before. Thus, the material covered is substantially greater in depth and variety than is normally attempted in a calculus course. In fact, we have attempted to inject new material into almost every chapter of the text as it appears on this site. Why have we done so? In part it is mere human frailty: to keep from going crazy while creating this material. Also, though, it is in order to maintain interest in the subject among those who have already been exposed to it. Finally, it is to show how easy it now is to absorb and use material that not long ago was utterly inaccessible to students, rarely taught, and when taught rarely mastered.