Nowadays a lot of people are keen to make presentations on computer to express their ideas. For example: teacher uses PPT and Flash to make courseware, financial staff uses it to show reports, designer demonstrates conception, and so forth. But presentation based on slideshow is missing the interaction and convenience of the traditional blackboard/whiteboard, which leads to such a bad result that both lecturers and audiences can only passively march forward following the scheduled architecture. This seems to be efficient, but is actually not as free and flexible as "a piece of paper + a pen".

HTTrack Website Copier (AKA: WinHTTrack, WebHTTrack, HTTrack for short) is a free and open-source websites crawling, downloading & offline browsing tool developed by Xavier Roche from France.

On hard disk, when you delete some folders, files or even an entire partition, all data is still existing in the same place where it was, and will always be there until overwritten. In fact, the deleting operation is just delete the pointer to the data on disk from MFT (Master File Table), so as to allow the operating system to perform writing operation there. Any data recovery software use this principle to work. Of course, you can delete the data truly and completely. But that requires you to ask special data eraser for help.

French writer Guy de Maupassant is one of the world's leading masters of short stories in the 19th century, Bel Ami (AKA: The History of a Scoundrel, A Ladies' Man) is the second and representative work of the only 6 full-length novels in his life with the highest thought and artistic achievement.

AutoCAD is undoubtedly the most popular and powerful CAD modeling software. But as a commercial software, it is really, really expensive. FreeCAD is a free, open-source, cross-platform and general-purpose 3D CAx (CAD, CAM, CAE), PLM modeling tool specially designed for home user/hobbyist, experienced CAD user, programmer or educator.