DGN files are drawings created by and supported by CAD applications such as MicroStation and Intergraph Interactive Graphics Design System. It is used for creating and saving designs for construction projects such as highways, bridges, and buildings. The format is similar to Autodesk’s DWG file format and is considered its competitor.
Files having extension .BMP represent Bitmap Image files that are used to store bitmap digital images. These images are independent of graphics adapter and are also called device independent bitmap (DIB) file format. This independency serves the purpose of opening the file on multiple platforms such as Microsoft Windows and Mac. The BMP file format can store data as two-dimensional digital images in both monochrome as well as color format with various colour depths.
You can also convert DGN into many other file formats. Please see the complete list below.