| IOst.a | 14 | Macintosh Micro Shell, plus standard IO consolidation for the systems below, excluding 5, 12, and the unnumbered generic C system. The enumeration is a conditional assembly selector for the indicated system. | ||
| Ioc.a | C | |||
| Iocrds.a | 1 | Unos, Charles River Data Systems | ||
| Iounis3.a | 4 | Unisoft, Torch | ||
| Iohp3.a | 5 | Hewlett Packard | ||
| Iomu3.a | 6 8 |
Unix System V, Motorola Unix System V, Stride |
||
| Ioat3.a | 7 | AT&T Unix | ||
| Iomin.a | 9 | Minimum | ||
| Iosun.a | 10 | Sun | ||
| Ioatari.a | 11 | Atari | ||
| Iomac.a | 12 | Unix System V, Macintosh II | ||
| Ioamiga.a | 13 | Amiga | ||
| Ionext.a | 15 | NeXT |