CAD, or computer-aided design and drafting (CADD), is the use of computer technology for design and design documentation. CAD software replaces manual drafting with an automated process.If you work in the architecture, MEP or structural engineering fields, you have probably used 2D or 3D CAD programmes. These programmes can help you to explore design ideas, visualise concepts through photorealistic renderings and simulate how a design will perform in the real world. AutoCAD software was the first CAD programme and it is still the most widely used CAD application.