| qch | Intuit Quicken for DOS Data File |
| qch | QT Compressed Help |
| qci | Cliq Accessories Phonebook Index |
| qck | Jigsaw 2 Quickcharts Data |
| qcl | Quark Color Library |
| qclk | QuickShow Clock Data |
| qcm | 3164 Emulator Quick Command |
| qcn | QPST Content |
| qct | Quick Chart Data |
| qd | Sharp MZ-series Emulator Quick Disk Data |
| qd0 | Omnis Quartz Segment 10 Data |
| qd3 | Omnis Quartz Segment 3 Data |
| qd4 | Omnis Quartz Segment 4 Data |
| qd5 | Omnis Quartz Segment 5 Data |
| qd6 | Omnis Quartz Segment 6 Data |
| qd8 | Omnis Quartz Segment 8 Data |
| qda | KaleidaGraph Data |
| qdat | QuickTime Install Cache |
| qdb | Quicken Data Backup |
| qdc | Quick Devis Database |
| qdd | Rimage QuickDisk Job Data |
| qdd | Snapform Designer Binary Data |
| qdes | DatabaseSpy Design Data |
| qdf | Quicken Data |
| qdf-backup | Intuit Quicken Data Backup |
| qdfm | Intuit Quicken for Mac Data File |
| qdfx | Intuit Quicken Financial Exchange File |
| qdi | Quanquest Data Mapping Data |
| qdi | Quicken Data Index |
| qdm | fsQCA Data |
| qdp | Quick and Dandy Plotter Data |
| qdt | Intuit Quicken v4 Data File |
| qdw | AnyQuest Questionnaire Definition Data |
| qef | Qubicle Exchange Data |
| qeff | QuickShow Effects Data |