What is the DC file format?
.dc is the native drawing file format of DesignCAD, a low-cost 2D and 3D CAD application originally developed by American Small Business Computers in the late 1980s and later acquired and published by IMSI/Design, LLC - the same company behind TurboCAD.
A .dc file stores vector CAD geometry in a proprietary binary container using little-endian byte ordering. It can hold lines, arcs, polylines, 3D wireframe and solid entities, layers, named blocks, and drawing-wide settings. Geometry is stored directly without compression or encryption. There is no publicly documented constant file signature, so .dc files are best identified by their DesignCAD origin and the .dc extension itself.
The format has a related older sibling: .dc2, a plain-text ASCII variant used for legacy 2D drawings. Newer DesignCAD versions migrated to .dcd and .dc3 as their primary native formats, making plain .dc a legacy extension today. For interoperability with other CAD tools, DesignCAD exports to DXF and DWG, the widely used AutoCAD interchange formats.
Note that .dc is also used, unrelated to DesignCAD, for SPICE DC analysis output files produced by circuit simulation software - a completely separate context sharing only the extension name.
Programs that open .dc files:
- DesignCAD (IMSI/Design) on Windows
- TurboCAD (IMSI/Design) on Windows
- TurboCAD Mac (IMSI/Design) on macOS
Security & safety
RISK: LOWDesignCAD .dc files are CAD drawing data and are safe to open in DesignCAD/TurboCAD. They are not executable. Download DesignCAD/TurboCAD only from IMSI/Design's official sites (imsidesign.com / turbocad.com) rather than repack/crack mirrors, which are a common malware vector for paid CAD software. The main practical confusion is the .dc name clash: confirm whether your file is a DesignCAD drawing or SPICE/other text output before troubleshooting.
Format details
in a nutshell- SPICE DC analysis output file - The .dc extension is also used by SPICE circuit simulators for DC (direct-current) analysis output data - a plain-text results file, unrelated to DesignCAD.
- Crazy Browser session / DreamCoder for Oracle file - Minor legacy uses: a Crazy Browser session file and DreamCoder for Oracle (PL/SQL) connection data have also used .dc.
Programs that open DC files
Windows2 apps
DesignCAD (IMSI/Design)
Paid Open the .dc directly in DesignCAD to view and edit the 2D/3D drawing; this is the native application.
TurboCAD (IMSI/Design)
Paid Import the DesignCAD geometry into TurboCAD (same vendor) for editing or to re-export to DWG/DXF. 
macOS1 app
TurboCAD Mac (IMSI/Design)
Paid On macOS use TurboCAD Mac to import DesignCAD-family geometry where supported, or to convert to DWG/DXF. Technical details
deep spec| Format type | Proprietary binary 2D/3D CAD drawing; a legacy plain-text ASCII variant (.dc2) also exists |
| Developer | IMSI/Design, LLC (originally American Small Business Computers) |
| Byte order | Little-endian |
| Encoding | Binary for the primary .dc format; the related .dc2 variant is plain ASCII text |
| Container | Proprietary DesignCAD record-based container - no standardised wrapper |
| Compression | None - vector geometry entities are stored directly, uncompressed |
| Typical file size | 10 KB - 10 MB, depending on drawing complexity and amount of 3D geometry |
| Geometry types stored | Lines, arcs, polylines, 3D wireframe and solid entities, layers, and named blocks |
| Drawing settings | Layer definitions, color assignments, units and coordinate-system settings embedded in the file |
| Platform | Windows (primary); macOS supported in limited/legacy capacity via TurboCAD Mac |
| File signature (magic bytes) | None publicly documented; files are identified by the .dc extension and DesignCAD origin |
| MIME type | application/octet-stream (no dedicated MIME type registered) |
| Superseded by | Newer DesignCAD native formats .dcd and .dc3; DXF and DWG for interchange with other CAD tools |
| Legacy status | Considered a legacy extension; modern DesignCAD versions default to saving .dcd or .dc3 files |
| Released | Late 1980s (DesignCAD by American Small Business Computers; later IMSI/Design) |
| Latest version | DesignCAD 2D/3D (current IMSI/Design release; native format newer .dcd/.dc3) |
| Specification | www.imsidesign.com |
DC conversions
Community Q&A
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