Mechanical computer aided-design software (MCAD) is used by machine designers and mechanical engineers to design and develop mechanical systems. MCAD software is also used in architectural and construction applications. Some mechanical computer-aided design software (MCAD) is a simple, two-dimensional (2D) wireframe program for creating engineering drawings or schematics. Other MCAD applications are complex three-dimensional (3D) products for developing accurate and dynamic models. These 3D MCAD applications may also provide different surface-modeling options and animation techniques. Sophisticated mechanical computer aided-design software (MCAD) can also take individual components and assemble them into a proposed design so that users can determine whether the components will work together successfully. Mechanical computer aided-design software (MCAD) may use a bottom-up or top-down approach. Beginning with a basic drawing and then building more elaborate designs is called bottom-up design. Top-down design approaches involve breaking down an existing product into single components. This approach allows mechanical designers to assess and evaluate the functionality of each individual component before assembling the new final product. Sometimes, MCAD software is used by electrical and electronic engineers for printed circuit board (PCB) design and wiring diagrams. Mechanical computer aided-design software (MCAD) also lends itself to manufacturing by graphically representing the layout of the plant or facility. Architectural, engineering, and construction (AEC) software is a type of mechanical computer-aided design software (MCAD) with applications for drafting and drawing, visualization, or project management and scheduling. Complex visualization packages allow designers to input sketches or other technical documents such as component drawings from a vendor, maps, or photos. The AEC software operator combines all the relevant pieces to produce drawings, specifications, materials lists, and even schedules for the project. Other specialized AEC software packages may include calculations for the size and strength of materials in a particular building configuration, or the effect of wind and other environmental stresses on a particular structure. Construction engineers may select MCAD software such as AEC applications to produce maps of a proposed site, to help documents based upon property surveys. Mechanical computer aided-design software (MCAD) is designed to run on personal computers (PCs) and often uses the Microsoft Windows or Linux operating systems. Web-based MCAD software is also available.