AS/400 History

The Beginning

The IBM System i, then known as the AS/400, was the continuation of the System/38 database machine architecture (announced by IBM in October 1978 and delivered in August 1979). The AS/400 removed capability-based addressing. The AS/400 added source compatibility with the System/36 combining the two primary computers manufactured by the IBM Rochester plant. The System/36 was IBM’s most successful mini-computer but the architecture had reached its limit. The first AS/400 systems (known by the development code names Silverlake and Olympic) were delivered in 1988 under the tag line “Best of Both Worlds” and the product line has been refreshed continually since then. Guy Dehond from Inventive Designers was one of the beta-testers of Silverlake. The programmers who worked on OS/400, the operating system of the AS/400, did not have a UNIX background. Dr Frank Soltis, the chief architect, says that this is the main difference between this and any other operating system.

The AS/400 was one of the first general-purpose computer systems to attain a C2 security rating from the NSA (Gould UTX/C2, a UNIX-based system was branded in 1986, and in 1995 was extended to employ a 64-bit processor and operating system.
The 1995 change-over from 48 to 64-bit required that all programs be ‘observable’, i.e. that the debugging information had not been stripped out of the compiled code. This caused problems for those who had bought third-party products that had no source and no observability. In 2008, the introduction of V6R1 caused similar problems, although this time IBM preferred to call it a “refresh”.
In 2000 IBM renamed the AS/400 to iSeries, as part of its e-Server branding initiative. The product line was further extended in 2004 with the introduction of the i5 servers, the first to use the IBM POWER5 processor. The architecture of the system allows for future implementation of 128-bit processors when they become available.
Although announced in 1988, the AS/400 remains IBM’s most recent major architectural shift that was developed wholly internally. Since the arrival of Lou Gerstner in 1993, IBM has viewed such colossal internal developments as too risky. Instead, IBM now prefers to make key product strides through acquisition (e.g., the takeovers of Lotus Software and Rational Software) and to support the development of open standards, particularly Linux. It is noteworthy that after the departure of CEO John Akers in 1993, when IBM looked likely to be split up, Bill Gates commented that the only part of IBM that Microsoft would be interested in was the AS/400 division. (At the time, many of Microsoft’s business and financial systems ran on the AS/400 platform, something that ceased to be the case around 1999, with the introduction of Windows 2000.
Logical PARtitioning
LPAR (Logical PARtitioning), a feature introduced from IBM’s mainframe computers, facilitates running multiple operating systems simultaneously on one IBM System i unit. A system configured with LPAR can run various operating systems on separate partitions while ensuring that one OS cannot run over the memory or resources of another. Each LPAR is given a portion of system resources (memory, hard disk space, and CPU time) via a system of weights that determines where unused resources are allocated at any given time. The operating systems supported (and commonly used) under the LPAR scheme are IBM i, AIX, and Linux.


Other features include an integrated DB2 database management system, a menu-driven interface, multi-user support, non-programmable terminals (IBM 5250) and printers, security, communications, client–server and web-based applications. Much of the software necessary to run the IBM System i is included and integrated into the base operating system.
Common Client-Server Support
The IBM System i also supports common client–server systems such as ODBC and JDBC for accessing its database from client software such as Java, Microsoft .NET languages and others.


AS400 Programming

Programming languages available for the AS/400 include RPG, assembly language, C, C++, Pascal, Java, EGL, Perl, Smalltalk, COBOL, SQL, BASIC, PHP, PL/I, Python and REXX. Several CASE tools are available: CA Plex (formerly AllFusion Plex) , Synon, IBM Rational Business Developer Extension, Accelerator, LANSA, Uniface and GeneXus.

Integrated Language Environment
The ILE (Integrated Language Environment) programming environment allows programs from ILE compatible languages (C, C++, COBOL, RPG, Fortran, and CL), to be bound into the same executable and call procedures written in any of the other ILE languages.
The IBM System i fully supports the Java language, including 32- and 64-bit Java Virtual Machines (JVM).
Commands in the Control Language (CL) are promptable using the keyboard F4 function key, and most provide cursor-sensitive help to make specifying command parameters simpler. All command names and parameter keywords are based upon uniform standardized and mostly 3-letter abbreviations for verbs and subjects, making for easy rendering and interpretation by the application developer, as opposed to other operating systems with often cryptic or inconsistent command names for related functions or command parameter switches. For instance, the parameter keyword to apply a text description to any object to be created or changed is spelled the same way for all such commands.
  • CRTUSRPRF, DSPUSRPRF, CHGUSRPRF, DLTUSRPRF – create, display, change, and delete user profile
  • CRTLIB, DSPLIB, CHGLIB, DLTLIB – Create, display, change and delete a library
  • ADDLIBLE, RMVLIBLE, CHGLIBL – Add or remove library list entry or change library list
  • CPYF, CRTF, DSPF, CHGF, DLTF – Copy, create, display, change, and delete file
  • WRKACTJOB – Work with Active Jobs
  • WRKSYSSTS – Work with System Status
  • STRSST, STRPASTHR, STRSBS – Start System Service Tools, start pass through (remote login), start subsystem
  • VRYCFG – Vary configuration, bring interfaces up or down
  • PWRDWNSYS – Power Down System
  • WRKSPLF – Work with spooled files
    For traditional business programming languages such as RPG, COBOL, and C, the IBM System i provides an interface to the integrated database that allows these languages to treat database tables much like other platforms treat ISAM or VSAM files.
Support for 5250 display operations is provided via display files, an interface between workstations, keyboards and displays, and interactive applications, as opposed to batch processing with little or no user interaction. ASCII terminals and PC workstations are equally and well supported, also via internet or LAN network access supplemented by either IBM or non-IBM communication software, for example TELNET or TELNET 5250.
IBM systems may also come with programming and development software like Programming Development Manager.

In 1986, System/38 announced support for Distributed Data Management Architecture (DDM). This enabled programs to create, manage, and access record-oriented files on remote System/36, System/38, and IBM mainframe systems running CICS. This support was extended into the AS/400 and its follow-ons. It was enhanced to support additional services that had been defined by DDM and to support AS/400-specific extensions, as allowed by DDM. In 1990, the AS/400 announced support for Distributed Relational Database Architecture, which is based on DDM.
The fact the AS/400 was created in 1988 and has been renamed several times hasn’t  helped in building the perception that it is a modern platform – but it most certainly is. More often identified today as IBM i, AS/400 remains a critical part of the computing infrastructure for many of the top organizations and ACOM customers.
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