| 71. | .ims | Create executable library data (IconForge) |
| 72. | .imt | Graphics (IMNET Graphics format) |
| 73. | .in | Input |
| 74. | .in$ | Installation file (HP NewWave) |
| 75. | .in3 | Input device driver (Harvard Graphics 3.0) |
| 76. | .inb | Test script (Vermont HighTest) |
| 77. | .inc | Include file (several programming languages) ◊ Include file subcircuit (Spice) |
| 78. | .ind | Database Index (dBASE IV) |
| 79. | .inf | Hypertext help system file (OS/2) ◊ Information (ascii file) ◊ Setup information, install script |
| 80. | .info | GNU info reader (output from texinfo) (unix) ◊ Icon Data (Amiga) |