IAB Internet Activities Board (Networking)
IAEA International Atomic Energy Agency
IANA Internet Assigned Numbers Authority (IANA@ISI.EDU)
IATA International Air Transport Association
IAU International Astronomical Union (Espacial)
IAUC IAU Circular (Espacial)
IBM Ingrained Batch Mentality
IBM International Business Machines, Inc. (nome de companhia)
IBM Itty Bitty Machines
IBT Illinois Bell Telephone
IC Integrated Circuit
IC Interexchange Carrier (Telefonia) (veja também IEC, IXC)
ICB Interstate Computer Bank
ICBM InterContinental Ballistic Missile
ICE In-Circuit Emulator
ICE International Cometary Explorer (Espacial)
ICI Imperial Chemical Industries
ICJ International Court of Justice
ICL International Computers Ltd.
ICMP Internet Control Message Protocol
ICP Integrated Channel Processor
ICP Inventory Control Points
ICRC International Cosmic Ray Conference
ID Idaho
ID IDentification
IDA Intercommunication Data Areas
IDA International Dark-sky Association (Espacial)
IDA International Development Association
IDDD International Direct Distance Dial (Telefonia)
IDE Interactive Development Environments, inc
IDF Intermediate Distributing Frame (Telefonia)
IDL Interactive Data Language (Espacial)
IDV Interlibrational Derived Vehicle (Espacial)
i.e. ???? (Latin(?): in other words (?))
IE Indo-European
IEC Inter-Exchange Carrier (Telefonia) (veja também IC, IXC)
IEE Institute of Electrical Engineers [UK]
IEEE Institute of Electrical and Electronic Engineers
IETF Internet Engineering Task Force
IF Intermediate Frequency 
IFB Invitation For Bids
IFC International Finance Corporation
IFC International Freighting Corporation
IFF Identification - Friend or Foe
IFF Interchange File Format
IFLA International Federation of Library Associations
IFR Instrument Flight Rules (Aviação)
IGES Initial Graphics Exchange Standard
IGM InterGalactic Medium (Espacial)
IGY International Geophysical Year
IGY International Geophysical Year (Espacial)
IHP Indicated HorsePower
IHS Integrated Hospital Support
IIA Information Industry Association
IIE Institute of Industrial Engineers
IIHF International Ice Hockey Federation
IIL Integrated Injection Logic
ILO International Labor Organization
ILS Instrument Landing System
ILV Industrial Launch Vehicle (Espacial)
IMF International Monetary Fund
IMHO In My Humble Opinion (Jargão usado na Net)
IMO In My Opinion (Jargão usado na Net)
IMP Interface Message Processor [ARPANET/MILNET] (substituído por PSN)
IMSL International Mathematical Subroutine Library
IN Indiana
INADS INitialization and ADministration System (Telefonia)
INRA Iesus Nazerenus Rex Iudaeorum (Jesus de Nazaré, Rei dos Judeus)
INRIA Institut National de Recherche en Informatique et Automatique
INS Immigration and Naturalization Service
INSTITUTE INSTITUTE's Name Shows That It's Totally Unrelated To EMACS
INTAP INteroperability Technology Association for information Processing
INWATS INward Wide Area Telephone Service (Telefonia)
I/O Input/Output
IO Input/Output (às vezes I/O)
IOC International Operating Center [Telefonia, US]
IOD Identified Outward Dialing
IOOF International Order of Odd Fellows
IOTA Infrared-Optical Telescope Array (Espacial)
IOTA International Occultation Timing Association (Espacial)
IOU I Owe you(U)
IP Information Provider (Telefonia)
IP Innings Pitched
IP Intermediate Point
IP Internet Protocol
IPC Inter-Process Communication
IPE Integrated Programming Environment
IPMS InterPersonal Message Services
IPS Inertial Pointing System (Espacial)
IPS Information Processing Standards
IPSE Integrated Project-Support Environment
IQ Intelligence Quotient (veja também EQ)
IR Index Register
IR Infra-Red
IRA Individual Retirement Account
IRA Irish Republican Army
IRAF Image Reduction and Analysis Facility (Espacial)
IRAS InfraRed Astronomical Satellite (Espacial)
IRBM Intermediate Range Ballistic Missile
IRDS Information Resource Dictionary Standard
IRDS InfraRed Detection Set
IRE Institute of Radio Engineers (velho nome para o novo IEEE)
IRM Information Resources Management
IRMS Information Resources Management Service
IRS Internal Revenue Service
IRTF Internet Research Task Force
IS Information Systems
IS International Standard [ISO] (além da fase DIS)
ISA Industry-Standard Architecture
ISAM Indexed Sequential Access Method
ISAS Institute of Space and Astronautical Science (Japan) (Espacial)
ISBD International Bibliographic Description
ISC Information Services Center
ISC International Switching Center
ISCH Interstitial-Cell-Stimulating Hormone (memo que LH)
ISDN Integrated Services Digital Network (Telefonia)
ISDT Integrated Systems Development Tool
ISEE International Sun Earth Explorer (usualmente ISEE-3)
ISF Information Systems Factory
ISFUG Integrated Software Federal User Group
ISI Information Sciences Institute
ISM InterStellar Medium (Espacial)
ISO Infrared Space Observatory (Espacial)
ISO International Organization for Standardization 
ISO International Standards Organization (Espacial)
ISODE ISO Development Environment
ISOO Information Security Oversight Office
ISPM International Solar Polar Mission
ISPM International Solar Polar Mission (novo Ulysses) (Espacial)
ISR Institute of Snow Research
ISRG Independent Space Research Group
ISV Independent Software Vendor
ISY International Space Year (Espacial)
IT Industrial Technology
IT Information Technology
ITC Inter-Task Communication
ITS Incompatible Timesharing System
ITT International Telephone and Telegraph
ITU International Telecommunications Union
ITUSA IT Users Standards Association
IUE International Ultraviolet Explorer (Espacial)
IUS Inertial Upper Stage
IUS Inertial Upper Stage (Espacial)
IUV Interlibrational Utility Vehicle (Espacial)
IXC Inter-eXchange Carrier (Telefonia) (veja também IC, IEC)
IXI International (pan-European) X.25 Infrastructure
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