| File extension Name |
extension description |
| .4 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .4 | Salt Lake City Game Music File |
| .4 | IBM Voice Type Language Script Data File |
| .4 | Screen Log File |
| .40 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .40 | AOL 4.0 Organizer (America Online, Inc.) |
| .400 | Designer Graphics File |
| .400 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .4000 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .4001 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .402 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .404 | FruityLoops Channel State File |
| .41 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .411 | Sony Mavica Data File |
| .42 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .42 | Salt Lake City Game Music File |
| .44 | Clipstream 32 Kb Stream |
| .45 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .45 | Salt Lake City Game Music File |
| .47 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .48 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .49 | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .49 | Salt Lake City Game Music File |
| .4A | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .4A3 | STABCAL (stability calculation for aqueous systems) File |
| .4A5 | STABCAL (stability calculation for aqueous systems) File |
| .4B | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .4B3 | STABCAL (stability calculation for aqueous systems) File |
| .4B5 | STABCAL (stability calculation for aqueous systems) File |
| .4BIT | GoDot |
| .4BT | GoDot Graphic |
| .4BW | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .4C$ | 4Cast/2 Data |
| .4C3 | STABCAL (stability calculation for aqueous systems) File |
| .4C5 | STABCAL (stability calculation for aqueous systems) File |
| .4CLR | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .4CM | ClickyMouse Macro Set (Pitrinec Software) |
| .4CX | 4th Dimension Carbonized Plug-in (4D, Inc.) |
| .4DB | 4th Dimension Database Structure (4D, Inc.) |
| .4DC | 4th Dimension Compiled Structure (4D, Inc.) |
| .4DD | 4th Dimension Database Data (4D, Inc.) |
| .4DF | 4th Dimension Database Windows Search Document (4D, Inc.) |
| .4DG | 4th Down Football Scout Game Data File (MoDi Software) |
| .4DK | OS/2 Saved SKF Format File (IBM) |
| .4DL | 4th Dimension Database Windows Log File (4D, Inc.) |
| .4DR | 4th Dimension Database Data (4D, Inc.) |
| .4DS | 4th Dimension Database Windows Data Segment (4D, Inc.) |
| .4DX | 4th Dimension Database Plug-in (4D, Inc.) |
| .4FI | 4th Dimension Database Windows ASCII Map (4D, Inc.) |
| .4FR | 4th Dimension Database Windows Apply Formula Document (4D, Inc.) |
| .4GE | Informix 4GL Compiled Code |
| .4GL | Informix 4GL Source |
| .4H3 | STABCAL (stability calculation for aqueous systems) File |
| .4KHZ | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .4LB | 4th Dimension Database Windows Label (4D, Inc.) |
| .4LK | 4th Dimension Database Windows Hot Link File (4D, Inc.) |
| .4MA | FileMaker Runtime Database (FileMaker, Inc.) |
| .4MD | Music File |
| .4MI | 4MI File (GTA4MODS.COM) |
| .4O3 | STABCAL (stability calculation for aqueous systems) File |
| .4O5 | STABCAL (stability calculation for aqueous systems) File |
| .4PK | Perfect Keyboard Macro Set (Pitrinec Software) |
| .4PP | PhotoParade Ver 4+ Slideshow (Callisto Corporation) |
| .4QR | 4th Dimension Database Windows Quick Report (4D, Inc.) |
| .4ST | 4th Dimension Database Windows Saved Set (4D, Inc.) |
| .4SW | 4DOS Swap File |
| .4T | Unknown Apple II File (found on Golden Orchard Apple II CD Rom) |
| .4TH | FORTH Source Code Program |
| .4UG | 4th Dimension Database Windows User/Groups Set (4D, Inc.) |
| .4V | Quartet Music File |
| .4VR | 4th Dimension Database Windows Saved Variable (4D, Inc.) |
| .4W | Four Winds Mah Jong Saved Layout/Game (Lagarto) |
| .4WD | WebMerge Data List File (Fourth World Media Corporation) |
| .4XM | 4X Movie Format |