| occ | DB/TextWorks List of BTX Records |
| occ | OptControlCentre Model |
| ocd | OCAD Map |
| ocd | OrgCon Organization Data |
| ocen | EdGCM OCEN Data |
| ocf | Object Craft File |
| ocf | Orbit Construction Data |
| och | Viewsat FTA Receiver Channel List |
| ocimf | OCIMF HVPQ Data |
| ocm | AOL Advertising Control Data |
| ocp | Orbit Composite Point Cloud |
| ocr | Orbit Composite Resources Data |
| ocr | Subtitle Workshop OCR Script |
| ocs | OCS Inventory NG Data |
| ocsmeet | Microsoft Lync Online Meeting Data |
| ocsp | HAProxy OCSP Data |
| oct | Radiance Octree |
| ocv | Optical Character Verification Data |
| ocw | Symantec ESM Oracle Configuration Watch Template |
| oc_ | Compressed OCX File |
| od | Atari Jaguar DSP Object Module |
| od | Atari Jaguar Envelope Definition Data |
| od | Atari Jaguar Sound Patch |
| od | Mascopt Data |
| od1 | Omnis Studio Database |
| od2 | Omnis Studio Database |
| od3 | Omnis Studio Database |
| od4 | Omnis Studio Database |
| od5 | Omnis Studio Database |
| od6 | Omnis Studio Database |
