| Abbreviation | Definition |
|---|---|
| IQY | Web query file (MS Excel) |
| IRC | IRCAM Sound format |
| IRIS | Bitmap graphics (Silicon Graphics RGB image file) |
| IRQ | I R q |
| IRS | Resource (WordPerfect) |
| IRTP | Graphics (Graphicon-2000 Interactive Real-Time PHIGS) |
| IS | Modula-3 Intermediate assembly file |
| ISD | RapidFile Spelling Checker dictionary |
| ISH | Compressed file archive (ISH) |
| ISO | An ISO image ( file.ISO ) is an archive file of an optical disc. |
| ISO | ISO-9660 table |
| ISP | Internet service provider settings (MS IIS) |
| IT | Impulse Tracker Music file |
| IT | InTalk Settings file |
| ITF | JPI TopSpeed Pascal Interface file |
| ITS | Internet Document Set |
| IV | 3D object (Open Inventor format) |
| IVB | Bitmap graphics (Truevision Targa format) |
| IVR | Live Picture Virtual Reality world |
| IVT | Information title (InfoViewer) |