IBM i Knowledge Base

What Is IBM i?

IBM i is the operating system that runs on IBM Power Systems hardware. It is the direct software descendant of OS/400, the operating system IBM shipped with the original AS400 in 1988, and it still runs applications written for that platform decades ago.

IBM i is the operating system that runs on IBM Power Systems hardware today. If your organization has ever described a system as "the AS400," the operating system doing the work is, in almost every current case, IBM i. IBM i is not a new platform: it is the current name for a software lineage that started as OS/400 in 1988, and it preserves compatibility with applications written across that entire history. For the naming history in detail, see AS400 vs IBM i.

IBM i in One Paragraph

IBM i is a general-purpose business operating system built around an integrated relational database, an object-based storage model, and a security architecture that operates below the application layer rather than being bolted on top of it. It runs exclusively on IBM Power Systems hardware, alongside AIX and Linux, but the vast majority of IBM i installations are dedicated production environments running business applications written in RPG, COBOL, or, increasingly, modern languages calling into the same database and objects.

What Makes IBM i Different

Three architectural features distinguish IBM i from general-purpose operating systems like Windows or Linux:

  • Integrated database: DB2 for i is built into the OS itself, not installed as a separate product, which removes an entire category of licensing, patching, and integration work common on other platforms.
  • Object-based architecture: Every resource on IBM i, including programs, files, and libraries, is a typed object managed by the OS, rather than a raw file on a generic filesystem. This is a major reason IBM i has a strong security and stability track record.
  • Single-level storage: IBM i addresses disk and memory as a single, flat address space, a design carried forward from the original AS/400 architecture that simplifies how the OS manages data.

IBM i's Lineage

IBM i traces directly back to OS/400, the operating system IBM shipped with the original AS/400 in 1988. The OS was renamed i5/OS in 2004 alongside a processor architecture refresh, then renamed again to IBM i starting with IBM i 6.1 in 2008. See OS/400 for that naming history in full. Current IBM i releases are 7.3, 7.4, and 7.5; see IBM i release history for the complete version timeline.

Who Runs IBM i Today

IBM i is concentrated in manufacturing, financial services, healthcare, retail, and government organizations running transaction-heavy business applications, many of which originated decades ago and have been maintained and extended ever since rather than replaced. See is AS400 still used? for the current installed base and industry breakdown.

Frequently Asked Questions

Is IBM i the same as AS400?
IBM i is the current name for the operating system that started as OS/400 on the original AS400 in 1988. In casual use, AS400 and IBM i refer to the same platform lineage. See AS400 vs IBM i for the precise distinction.
What hardware does IBM i run on?
IBM i runs exclusively on IBM Power Systems hardware, including current Power10 and Power11 generations. It does not run on x86 or other non-Power hardware.
What database does IBM i use?
IBM i uses DB2 for i, a relational database integrated directly into the operating system rather than installed as a separate product.
What programming languages run on IBM i?
RPG and COBOL are the traditional languages for IBM i business applications, and both remain in wide production use. IBM i also supports Java, PHP, Python, Node.js, and other modern languages, which can access DB2 for i and IBM i objects alongside legacy code.