CAD

CAD is the pencil's successor three times over. First-generation tools digitised drafting: lines, arcs and text on electronic sheets, faster to edit and copy than paper but carrying no more meaning. 3D systems added geometry that could be coordinated, visualised and measured. Data-centric systems — plant design suites, BIM authoring tools — made the objects primary: the model as database, the drawings as generated views. All three generations remain in production use, often within one company, which is why "we have it in CAD" is a statement that means almost nothing until the generation is specified.

The industry's stock of CAD legacy is its own subject. Decades of DWG and station files hold enormous embedded effort — and, for the older generations, hold it as geometry whose meaning lives in conventions, layer names and the memories of the people who drew it. Format longevity, tool obsolescence and the difference between having the file and having the information are problems every long-lived owner eventually funds, usually during a revamp that needed the information rather than the file.