| 31. | .dc | CAD file (DesignCAD) ◊ DC outout (Spice) |
| 32. | .dc2 | CAD file (DesignCAD) |
| 33. | .dc5 | Drawing (DataCAD) |
| 34. | .dca | Document Content Architecture text file (IBM DisplayWrite) ◊ Visual Basic Active designer cache |
| 35. | .dcd | Document Content Description file (XML) |
| 36. | .dcf | Data file (Dyadic) ◊ Disk image file |
| 37. | .dcim | Digital Imaging and Communications in Medicine (image and data) |
| 38. | .dcl | Delphi Component Library (Borland Delphi) |
| 39. | .dcm | Bitmap graphics (Digital Imaging and Communications in Medicine image file format) |
| 40. | .dcp | Data CodePage (OS/2) ◊ Device code page (OS/2) ◊ default codepage file (ArcView) |