CAD can be defined as use of computers system to assist in creation, modification, analysis or optimisation of design .it is the acronym for Computer Aided Design(CAD) or Computer Aided Drawing (CADD).Both hardware and software inside computer helps to carry out whole process of AutoCAD. CAD software is programmed to carry out specific function. Depending upon the type of the firm or the company, they will choose the CAD software that can perform particular application right from heat transfer calculation to analysis of stress strained subjected of the components.There are many CADsoft wares available in market like AutoCAD, CADopia, SolidWorks, Catia, MathCAD, QuickCAD. Among these Auto CAD 2009 is most popular and latest software used now a days .Other software’s are quite cheap in usage.CAD systems allow an engineer to view a design from any angle with the push of a button and to zoom in or out for close-ups and long-distance views. In addition, the computer keeps track of design dependencies so that when the engineer changes one value then all other values that depend on it are automatically changed accordingly.CAD software are generally used by architects,draftsman, engineers and artist to create drawing or technical illustration like 2d drawing or 3d models.

Nowadays there are many free CAD softwares available in market like 3D Slash.

K-3D.
MeshMixe
Sketchup
Wings3d
3d crafter

For any CAD work requires a software package and many a times graphic card need to be installed.Graphic kernel is considered as main component of software package .Also another important element GUI,it’s used for getting user input and displaying the CAD geometry.

BENEFITS OF CAD

Flexibility in CAD: – Unlike in manual drafting where separate information onto individual transparent overlays but in CAD layers are equivalent to transparent overlays where one can display, edit, and print layers separately or in combination.

Easy drawing in CAD:-In cad size and resolution can be changed by zooming in or zooming out display size.However in manual ,size and resolution remains fixed.

Efficiency increases:– In manual drawings efficiency is not guaranteed as drawing tools include pencils, scales, compasses, parallel rules, templates, and erasers. Repetitive drawing and editing tasks must be done manually.But in CAD there are variety of drawing tools that create lines, circles, spline curves, and more. One can easily create other similar objects or move, copy, offset, rotate, and mirror objects

Accuracy increases: In manual drafting accuracy is not defined as one should draw objects carefully to ensure correct size and alignment. Objects drawn to scale must be manually verified and dimension ed. But in cad there are many methods to obtain exact dimensions. The simplest method is to locate points by snapping to an interval on a rectangular grid.