| ck9 | Cook'n Cookbook Backup |
| cka | Comfort Keys Database |
| cki | Ansys Chemkin Kinetic Data |
| cki | Off by One Web Browser Cookie Data |
| ckl | DISA STIG Checklist |
| ckn | Disk Doctors CK Support Info File |
| ckp | Ingres Database Checkpoint Data |
| ckp | PSI-BLAST Checkpoint Profile Data |
| cks | PSI-BLAST Checkpoint Sequence Data |
| ckt | Ansys Chemkin Thermodynamic Data |
| ckt | B2-Spice Circuit Design |
| ckt | Crocodile Clips Data |
| ckv | CheckVision Database |
| cky | DSOrganize Data |
| ckz | QuickSFV Checksum Database |
| cl | Carlson Survey Centerline File |
| cl | IconUtils Cursor Library |
| cl | QIP Contact List Data |
| cl2 | Hy-Tek Meet Manager Results Data |
| cl7 | Free Clipboard Viewer Saved Data |
| clam | Adobe InDesign User Dictionary Data |
| classlist | SMART Notebook Class List |
| clb | Corel Mosaic 5.0 Library |
| clb | ICQ Contact List Data |
| clb | NoteTab Clipbook Library |
| clbu | Android Call Log Backup |
| clbx | MP3 Automagic CD Cover Creator Label |
| clc | Corel Mosaic 5.0 Catalogue |
| clc | Schedule Plus Habits Mission Statement Data |
| clc | UltimaCalc Data |
