There are many different software programs that have been given the acronym CAD (Computer-Aided Design). Some have endured the test of time and others have disappeared from the marketplace. If you have a historical interest in the subject of CAD I  would recommend the following links.
  1. Ivan Sutherland the “father of computer graphics”
  2. Computer-aided design software
  3. CAD Software – History of CAD/CAM

This page and its linked sub-pages are devoted to “all things related to Modeling in CAD.” This includes wireframe 2D sketch and 3D modeling with lines, curves, constraints, etc., as well as 3D surface and solid modeling. These pages and their associated links contain valuable information and instruction on part or component modeling, assembly or system modeling, and the dimensioning and drafting of working drawings for parts and assemblies.

Introduction to Engineering Design, Modeling and Graphics

Is a course for new and aspiring mechanical, aerospace, and automotive engineers. Navigate to the sub-page Eng. Design, Model … to find a full course description, syllabus, assignments, projects, etc.   All materials and topics are presented and taught in the context of learning and understanding modern Computer-aided Design (CAD), sometimes referred as 3D CAD. This educational course teaches core ASME and ISO design and drafting standards. The serious student will learn how to create and model 3D mechanical parts and assemblies, and how to create and annotate their designs into part and assembly working drawings. Here are a few examples of mechanical part design modeling problems that were assigned to past students.

Brake peddle     Emergency Foot Brake

wheelrim            Wheel Rim

turbine blade   Turbine Blade

Here are examples of previous assembly modeling projects.

Pipsqueak Air Engine     Pipsqueak Air Engine

Elbow Air Engine   Elbow Air Engine

Final_Render_Wright_Flyer     Wright Flyer

Here is an example part or component drawing.

Valve Body Part Drawing      Valve Body

An example of an assembled assembly drawing followed by an exploded assembly drawing.

Elbow Engine Assembled Drawing     Elbow Engine

Elbow Engine Exploded Drawing    Elbow Engine