CAD software

Computer-aided design (CAD) software replaces manual drafting with on-screen construction of accurate technical drawings and models. Instead of drawing on paper, a designer builds geometry from mathematical primitives, so dimensions remain exact and can be edited, copied and scaled without redrawing. CAD is fundamental to architecture, product design, mechanical and civil engineering, electronics layout and manufacturing, where drawings must carry precise measurements and annotations.

CAD packages fall into broad families. Two-dimensional drafting tools handle plans, sections and schematics. Three-dimensional solid and surface modellers build volumetric parts that can be checked for interference, measured for mass properties, or sent to manufacturing. Parametric modellers, common in mechanical design, let dimensions and relationships be defined as editable parameters so that changing one value updates the whole model. Building information modelling (BIM) extends this idea for architecture by attaching data to building components.

The best-known product is Autodesk's AutoCAD, whose DWG and DXF formats are widely used for exchanging drawings. Other major systems include MicroStation, SolidWorks, CATIA, Siemens NX, PTC Creo and the free, open-source FreeCAD, alongside lighter tools such as TurboCAD, DataCAD and Vectorworks. Because each program has its own native format, neutral exchange formats — DXF for 2D, and IGES or STEP for 3D — are used to move geometry between different applications. Many CAD tools also support scripting and add-on programming for automating repetitive work.

Frequently asked questions

What is the difference between 2D and 3D CAD?

2D CAD produces flat drawings such as plans and schematics, while 3D CAD builds volumetric models that can be rotated, measured and analysed in three dimensions.

What does parametric modelling mean?

It means the model is defined by editable parameters and constraints, so changing a dimension automatically updates the related geometry.

Are there free CAD programs?

Yes. FreeCAD is a well-known open-source parametric 3D modeller, and several other free or low-cost drafting tools are available for 2D work.