Is a new concept to designing aided through computers. Different software are now available that can make your designing works so easy. No more need to buy continuous streams of paper, or throw away poor work designs. With CADs you can just change what was wrong without affecting the actual design flow just like using ms word to type letters.
One such CAD for engineers and architects are AutoCAD and Solidworks.
Try them out and you will surely not be disappointed in your designing days.