IBM i is an operating system developed by IBM for the purpose of powering mission-critical business applications. It replaces the i5/OS and OS/400 operating systems but maintains application compatibility across these technology generations. For instance, applications built for OS/400 can often run on the latest IBM i systems without explicit recompilation, even though the hardware is vastly different.
IBM i runs on IBM Power Systems, along with IBM AIX and Enterprise Linux.


IBM designed IBM i as a "turnkey" operating system, requiring little or no on-site attention from IT staff during normal operation. As such, it has been described as "the driverless variant of IT infrastructure." For example, IBM i has a built-in Db2 database which does not require separate installation. Mass storage can be RAIDed or mirrored; when either of those options is configured, one or more disk can be replaced without interrupting work. System administration is wizard-driven. Automatic self-care can schedule all common system maintenance, detect many failures and order spare parts and service automatically. Organizations using IBM i sometimes have a pleasant when comparing the overhead of cost of system maintenance on other systems. The overall total cost of ownership for IBM i on IBM Power Systems is dramatically lower than two competing platforms, like Windows/SQL Server and Linux/Oracle, primarily due to the lack of system management personnel needed; integrated components also lower the TCO.
IBM i programs, like System/38 programs before them, contain both processor-independent "virtual" binary code and processor-dependent executable binary code. Compilers for IBM i produce the processor-independent code as their output; the operating system automatically translates the processor-independent code into the processor-dependent code as needed, without the need for source code or attention by IT personnel. Notably, when migrating from a legacy processor, if automatic migration is configured and if the original program was created with normal options, the system will rebuild the executable code automatically and in just a few seconds. Migration consists of taking a backup from the old computer, and restoring it on the new.
The system was one of the earliest to be object-based. Unlike traditional operating systems like Unix and Windows NT there are no files, only objects of different types. The objects persist in very large, flat virtual memory, called a single-level store.
IBM i offers an upgrade path so that application software written for previous operating systems on IBM System i can be migrated to current supported hardware without needing to be modified or recompiled. To do so, it provides an abstract interface to the hardware via layers of low-level machine interface code or Microcode that reside above the Technology Independent Machine Interface and the System Licensed Internal Code or kernel.

IBM software technologies

IBM i includes numerous software technologies

Application development

IBM Portable Application Solutions Environment for i enables port of IBM AIX applications to the IBM i platform.
PASE for i provides an integrated AIX runtime environment on the IBM i, including three industry-standard and defacto-standard shells and utilities for a powerful scripting environment, enabling many AIX applications to run on the IBM i operating system with little or no change. AIX programs are binary compatible with IBM i when using PASE. PASE is essentially "an operating system within an operating system", supporting the most recent stable version of AIX. Many AIX 5L compatible binaries may be executed without modification or recompilation in the PASE environment. Exceptions to this are programs that contain direct calls to AIX kernel based APIs as there is no AIX kernel in PASE. Programs can be built directly in place with the GNU Compiler Collection, or alternatively with the IBM XL C/C++ compilers. Support is provided for running both 32-bit and 64-bit AIX executables.
Integrated Web Services for i enables Integrated Language Environment applications to perform in the web services and service-oriented architecture arena.
Net.Data for i is a server-side scripting language that extends web servers by enabling the dynamic generation of web pages.
IBM InfoSphere Data Architect is a collaborative enterprise data modeling and design solution.

Management interfaces

IBM Navigator for i is a web-based interface to a family of products providing a comprehensive set of system management, performance analysis, database, Apache web server, and WebSphere Application Server features for IBM i.
IBM i Access Client Solutions is a Java-based client and a user, development and systems management interface solution that runs on Linux, macOS and Windows to provide 5250 emulation to run host applications. The Web-based IBM i Access Client solution enables desktop and mobile device users to connect to IBM i via web browsers.

Networking and communications

TCP/IP on IBM i offers TCP/IP applications, protocols, and services to direct the flow of data in and out of the network.

Open-source software

Open-source software available includes Apache HTTP Server, OpenSSL, Java, Ruby, PHP, Python, Node.js, gcc, Nginx, Git, and hundreds of other packages. In 2018, IBM made available the Yum package manager and the capability to install open-source software via RPM packages. Formal support for many packages is available from IBM and partners.

Programming languages

The OS supports many languages including RPG, assembly language, C, C++, Pascal, Java, EGL, Perl, Smalltalk, COBOL, SQL, BASIC, PHP, PL/I, Python, REXX, Ruby, PHP, Python, Node.js, Lua, R, , and more.

Development tools

is the integrated development environment published by IBM for working with many technologies such as RPG. Industry-standard tools can be used for programming as well, and are especially popular when using open source languages. Several other tools are available from independent software vendors, many of which are listed in the .

IBM i history and versions

IBM i release 6.1 was announced April 2, 2008 with IBM POWER Systems. This release numbering contrasts with previous version identifier format VxRxMx of prior versions in its lineage. This release number demonstrated the ability for applications built on previous technologies to continue their functional usage on the new Power Systems technology.
With 7.1, IBM started delivering more updates to the operating system via Technology Refreshes. These Technology Refreshes enable further value to the operating system without the need of incurring point releases and allowing customers longer periods between upgrades. For 7.1, Technology Refresh 11 was released in October 2015. IBM i 7.2 Technology Refresh 9 was released in September 2018. IBM i 7.3 Technology Refresh 6 was released May 10, 2019.
Version 7.2 was released in May 2014.
Version 7.3 was released in April 2016.
The latest version of IBM i is 7.4, announced on April 23, 2019 and released on June 21, 2019.
Every release of IBM i has a finite support period.

IBM i versions

Lineage of previous technology (CPF, OS/400 and i5/OS) and versions

As IBM i supports running legacy applications built for CPF on System/38, OS/400 on AS/400, or i5/OS on iSeries respectively), the lineage of the platform is often associated with those technologies as well.
In 1978, the fundamental architectural principles of what would become IBM i operating system were introduced with CPF operating system for the IBM System/38, developed by IBM team in Rochester, Minnesota, led by IBM chief scientist Frank Soltis,. Fortress Rochester: the Inside Story of the IBM iSeries, NEWS/400 Books.
In 1988, OS/400 Release 1 drew upon and extended the heritage of CPF to power the Application System/400 line of midrange computers.
For the period 1988-2006, OS/400 versions 1 through V5R3 were released as AS/400 underwent rebranding to Advanced System/400 and IBM eServer.
In 1999, IBM introduced logical partitioning with i5/OS to support multiple virtual systems on a single hardware footprint.
In 2006, the operating system at V5R4 was named i5/OS for the newly introduced System i servers, which IBM marketed until 2008.

User groups

User groups have played a major part in the evolution of IBM i. COMMON is the world’s largest professional association of IBM technology users. It provides independent education, certification, advocacy and networking among users, IBM and related third-party solution providers. The Large User Group, whose membership consists of major corporations, is a major influence for current and future development of IBM i. Both COMMON and LUG work with IBM regularly to help provide constructive feedback and perspective to IBM i platform direction. The Young i Professionals is a subset of COMMON that has been significant in influencing the direction of the IBM i.