Unveiling the Legacy of the IBM AS/400: A Journey Through Time

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In an era dominated by rapid technological evolution, the IBM AS400 stands out as a monumental figure in the history of computing. Initially launched in 1988, this family of mid-range computer systems revolutionized the way businesses approached data processing, offering unparalleled reliability, ease of use, and integration capabilities. Today, we embark on a journey to unravel the mysteries of the AS/400, shedding light on its origins, architectural brilliance, and enduring legacy. Through this exploration, we aim to provide a comprehensive understanding of its significance in shaping the technological landscape.

Table of Contents:

  1. What was the IBM AS/400?
  2. History of the IBM AS400
  3. System Architecture and Hardware
  4. Software Ecosystem and Applications
  5. Impact on Business Computing
  6. Transition to IBM iSeries and Future Paths
  7. References
The Legacy of the IBM AS/400 System

1. What was the IBM AS/400?

Introduced by IBM in 1988, the AS/400 (Application System/400) was designed to consolidate a variety of business functions into a single, integrated system. Its architecture was a departure from the norm, employing a unique combination of hardware and software that could run applications from older systems while embracing new computing technologies.

AS 400 stands for Application System 400, a midrange IBM server computing platform for business computing. AS/400 uses 64-bit RISC technology, supports Systems Network Architecture (SNA) and runs the OS/400 operating system.

Traditional SNA user interfaces to AS/400 systems use either text-based 5250 terminals or desktop PCs running 5250 emulation software. But IBM has released a version of OS/400 that turns the AS/400 into a Web server and allows AS/400 applications to be interfaced using TCP/IP from a standard Web browser such as Microsoft Internet Explorer.


The AS 400 was originally based on a custom IBM CISC CPU which had an instruction set architecture, known as Internal MicroProgrammed Interface (IMPI), similar to that of the IBM System/370. It was later migrated to a POWER-based RISC CPU family eventually known as RS64.

2. History of IBM AS/400

The story of the IBM AS/400, commonly referred to as “AS400” or “AS 400,” is a fascinating chapter in the annals of computing history, marking a period of significant transition and innovation within IBM and the wider tech industry. Launched on June 21, 1988, the AS/400 was more than just a new product; it was a bold statement by IBM on the future of business computing, integrating the best of its midrange computing technologies into a single, unified platform.

2.1 Origins and Development

The AS/400’s genesis was part of IBM’s grand vision to consolidate its diverse range of midrange systems, including the System/3, System/34, System/36, and System/38, into a singular, more advanced computing platform. This strategic move was aimed at simplifying the technology landscape for businesses, making it easier to integrate, manage, and scale operations across various domains. The development of the AS/400 was a massive undertaking, involving a significant investment in research, development, and market analysis to ensure the new system met the evolving needs of businesses.

Central to the AS/400’s development was the decision to base it on a new, object-oriented operating system, OS/400. This choice underscored IBM’s commitment to reliability, security, and backward compatibility, ensuring that businesses could leverage their existing software investments while tapping into the latest computing technologies. The OS/400 was designed to run on a novel hardware architecture, featuring the CISC (Complex Instruction Set Computer) processors, which later transitioned to the more powerful and efficient RISC (Reduced Instruction Set Computer) architecture with the AS/400 Advanced Series.

2.2 A Revolutionary System

The launch of the AS/400 was met with widespread acclaim, quickly establishing it as a cornerstone of IBM’s product lineup. It offered an unprecedented level of integration, boasting an internal relational database, DB2, integrated networking, and support for multiple programming environments. This all-in-one approach allowed businesses to dramatically streamline their IT operations, reducing costs and complexity while enhancing overall productivity and performance.

IBM AS 400 models

2.3 Role in IBM’s Product Line Evolution

The AS/400 played a pivotal role in IBM’s midrange computer strategy, bridging the gap between the company’s larger mainframe computers and its personal computer offerings. Its success spurred IBM to continue innovating in this space, leading to the development of subsequent generations like the IBM eServer iSeries in 2000, and later the IBM System i in 2006. Each iteration built upon the AS/400’s foundational principles of integration, reliability, and ease of use, while introducing new technologies and capabilities to keep pace with the changing demands of the business world.

Throughout its evolution, the AS/400 and its successors remained true to the original vision of providing a robust, versatile computing platform capable of adapting to the needs of businesses of all sizes. Its legacy is seen in the modern IBM Power Systems and the IBM i operating system, which continue to offer a direct lineage back to the pioneering work of the AS/400.

The history of the IBM AS/400 is not just a tale of technological achievement; it’s a testament to IBM’s enduring commitment to innovation, customer focus, and the drive to transform business computing. By understanding its origins and development, we gain insight into the principles that have guided the evolution of enterprise computing to this day.

3. System Architecture and Hardware of the IBM AS/400

The IBM AS/400 stands as a hallmark of innovative design in the realm of mid-range computing systems. Its architecture and hardware composition broke new ground at its launch, introducing a seamless integration of software and hardware that was ahead of its time. This chapter delves into the unique design principles of the AS/400, the OS/400 operating system that powered it, and the robust hardware that underpinned its success.

3.1 Innovative Design Principles

The architecture of the AS/400 was revolutionary, primarily because of its integrated approach. Unlike other systems of the era that treated hardware and software as distinct entities, the AS/400 was designed as a comprehensive system where the hardware and software were inextricably linked. This tight integration resulted in unparalleled reliability, performance, and ease of use.

One of the core design principles of the AS/400 was its use of a virtual machine environment, made possible by the OS/400 operating system. This meant that applications running on the AS/400 did not interact directly with the hardware but with a virtual representation of it. This abstraction layer ensured that applications could run independently of the underlying hardware, allowing for significant hardware upgrades and changes without impacting the software running on the system.

3.2 The OS/400 Operating System

The OS/400 operating system was a key component of the AS/400’s success. It was an object-oriented OS that introduced a level of security and stability unmatched at the time. The OS was capable of automatically managing system resources, which significantly reduced the need for manual intervention in system administration. Its integrated database, IBM Db2 for i, was another standout feature, providing robust data management capabilities directly out of the box.

OS/400 also supported a wide range of programming languages, from legacy languages like RPG and COBOL to modern ones such as Java, enabling businesses to leverage their existing codebase while embracing new development paradigms.

3.3 Robust Hardware

The initial AS/400 models were built on a Custom Complex Instruction Set Computer (CISC) architecture, which provided the flexibility and power needed to support the system’s integrated approach. However, IBM didn’t stop there. Recognizing the need for greater performance and efficiency, IBM transitioned the AS/400 to a more advanced Reduced Instruction Set Computer (RISC) architecture with the introduction of the AS/400 Advanced Series in the early 1990s. This shift to RISC technology, specifically the POWER architecture, marked a significant leap in processing power and efficiency, ensuring that the AS/400 platform remained competitive in the face of rapidly advancing computing technologies.

The hardware was also characterized by its high level of integration. Early models featured everything from processors and memory to disk storage and networking capabilities all within a single system. This all-in-one design philosophy reduced complexity and made the AS/400 an attractive option for businesses looking to streamline their IT infrastructure.

3.4 Legacy and Evolution

The system architecture and hardware of the AS/400 were not just innovative for their time; they laid the groundwork for future developments in enterprise computing. The principles of integration, reliability, and ease of use that defined the AS/400 continue to influence the design of modern computing systems. The evolution of the AS/400 into the IBM iSeries and later the IBM Power Systems showcases the lasting impact of the AS/400’s foundational design principles.

In conclusion, the system architecture and hardware of the IBM AS/400 represented a significant milestone in the evolution of business computing. Its integrated design, powered by the advanced OS/400 operating system and supported by robust hardware, established a new standard for reliability, performance, and ease of management. The legacy of the AS/400’s innovative design principles continues to resonate in today’s computing platforms, underscoring its role as a pioneering system in the history of technology.

3.5 AS400 Working

Are you curious to watch IBM AS/400 working?

AS/400 (IBM) Tutorial – Navigation, Menus and FKeys

4. Software Ecosystem and Applications

The IBM AS/400’s robustness was not just a result of its innovative hardware architecture but also its comprehensive software ecosystem. Central to this ecosystem was the OS/400 operating system, a suite of key software applications, and a set of development tools that collectively defined the system’s capabilities and contributed to its widespread adoption across various industries.

4.1 The OS/400 Operating System

The OS/400 operating system set the stage for the AS/400’s success. It was a highly stable and secure environment that supported a range of business applications directly out of the box. Its object-oriented design enabled seamless system updates and maintenance, ensuring that the system could evolve without disrupting ongoing business operations. The OS/400 also featured an integrated database, IBM Db2 for i, offering sophisticated data management and analytics capabilities.

4.2 Key Software Applications

The AS/400 was renowned for its wide array of software applications tailored to various business needs. These applications ranged from financial management and human resources to manufacturing and supply chain management. IBM and third-party developers created a rich ecosystem of applications that were specifically optimized for the AS/400 environment, leveraging the system’s integrated architecture for enhanced performance and reliability.

Popular applications included JD Edwards World for enterprise resource planning (ERP), which helped businesses streamline their operations, and IBM WebSphere Development Studio for developing and managing web-based applications. The platform’s versatility made it ideal for businesses of all sizes, from small firms to large multinational corporations.

4.3 Development Tools

IBM provided a comprehensive set of development tools for the AS/400, facilitating custom software development and system customization. These tools supported a variety of programming languages, including RPG, COBOL, C, C++, Java, and SQL. The Integrated Language Environment (ILE) was a significant advancement, offering a modular approach to application development and enabling developers to use multiple languages within the same program.

The IBM Rational Developer for i was another crucial tool, providing an integrated development environment (IDE) for modern application development on the AS 400. These tools ensured that businesses could not only leverage existing applications but also develop bespoke solutions tailored to their specific needs.

5. Impact on Business Computing

The introduction of the IBM AS/400 marked a pivotal moment in the history of business computing. Its impact was profound, transforming business processes and operations through its unparalleled integration, reliability, and versatility.

5.1 Transforming Business Processes

The AS/400’s integrated design philosophy simplified IT infrastructure for businesses, consolidating disparate systems into a single, unified platform. This consolidation enabled more streamlined operations and reduced the complexity and cost of IT management. Businesses could now rely on a single system for a wide range of applications, from core business functions like ERP, customer relationship management (CRM), and supply chain management (SCM) to more specialized applications.

5.2 Success Stories and Case Studies

One notable success story is that of a major retail chain that implemented the AS400 to manage its inventory and sales processing across hundreds of stores. The system’s reliability and real-time processing capabilities enabled the retailer to maintain accurate inventory levels, process transactions efficiently, and improve customer satisfaction.

Another case study involves a global manufacturing company that used the AS/400 for its entire production and distribution process. The AS/400’s robust database and application integration capabilities allowed the company to optimize its supply chain, reduce production costs, and improve time-to-market for its products.

5.3 Legacy and Continued Influence

The legacy of the AS/400 in business computing is its demonstration of the power of integration and the importance of building systems that are reliable, secure, and capable of evolving with technological advancements. Many of the principles that the AS/400 introduced have become standard expectations in today’s enterprise computing environments.

The AS 400 showed that technology could be a transformative force in business, not just by automating existing processes but by enabling new ways of working and innovating. Its impact is still felt today, as the principles it championed continue to influence the development of modern enterprise systems and solutions.

6. Transition to IBM iSeries and Future Paths

The evolution of the AS/400 into the IBM iSeries and subsequent platforms marks a fascinating journey of technological advancement and adaptation. Launched in 2000, the IBM iSeries represented a significant leap forward, building upon the AS/400’s foundation while introducing new capabilities to meet the changing demands of the business world.

6.1 The iSeries Evolution

The iSeries continued the AS/400’s legacy of integration and reliability but with enhanced performance, scalability, and flexibility. It introduced support for Web-based applications and e-business, reflecting the growing importance of the internet in business operations. The iSeries also embraced open standards and technologies, including support for Linux and Java, making it a more versatile and adaptable platform.

6.2 Future Paths and Modern Computing Platforms

The transition from the iSeries to the IBM System i and eventually to the IBM Power Systems showcased IBM’s commitment to innovation and its responsiveness to market trends. Today’s IBM Power Systems inherit the AS/400’s ethos of reliability and integration but are designed to support modern computing needs, including big data analytics, cloud computing, and artificial intelligence.

This evolution underscores the enduring legacy of the AS/400 in shaping IBM’s approach to enterprise computing. It remains a testament to the power of forward-thinking design and the importance of building systems that can adapt over time to meet the ever-evolving needs of businesses.

7. References