| 1. | H | Header File, mostly belonging to .C or .CPP file |
| 2. | H-- | |
| 3. | H! | Help database (Flambeaux Help/Perfect Database) |
| 4. | H++ | |
| 5. | HA | Compressed file archive (HA) |
| 6. | HAL | Data file (Hyper Access Lite OS/2) |
| 7. | HAM | Novell NetWare disk drivers NPA |
| 8. | HAP | Compressed file archive (HAP) |
| 9. | HBK | |
| 10. | HBM | |
| 11. | HC | |
| 12. | HCOM | |
| 13. | HDF | Hierarchical Data Format bitmap image (NCSA) Help file (Help Development Kit Procomm Plus alternate download file listing |
| 14. | HDR | Pc-File+ database HeaDeR Egret datafile Message HeaDeR (Procomm Plus/1st Reader) |
| 15. | HDS | |
| 16. | HDW | Harvard Draw vector image |
| 17. | HDX | Help index (AutoCAD/Zortech C++) |
| 18. | HED | |
| 19. | HEL | |
| 20. | HEP | Novell NetWare Help Librarian data file |