| I/O | input/output |
| IBM | International Business Machines |
| ICAPI | Internet Connection Application Programming Interface |
| IDEA | International Data Encryption Algorithm |
| IDL | interface definition language |
| IEEE | Institute of Electrical and Electronics Engineers |
| IETF | Internet Engineering Task Force |
| IIOP | Internet Inter-Object Request Broker Protocol |
| IP | Internet Protocol |
| IPSec | IP Security |
| ISP | Internet service provider |
| IT | information technology |