Pl/I, 333 | IBM OS/390 specification

Chapter 15. PL/I

The PL/I language compiler implemented on VSE is the DOS PL/I Optimizing Compiler (5736-PL3). In MVS, the PL/I language is implemented by the OS PL/I Optimizing Compiler Version 1 (5734-PL3), and OS PL/I Version 2 Optimizing Compiler (5668-910).

As the OS PL/I Version 2 Optimizing Compiler implements more of the PL/I language than Version 1 does, most source programs compiled on the VSE compiler can be compiled on either of the two MVS compilers with a minimum amount of change.

Note: The most current version of PL/I is PL/I for MVS & VM Version 1, Release

1.This compiler produces object code designed to run under Language Environment, a common run-time environment for several languages on this platform. Please refer to the IBM PL/I for MVS & VM Compiler and Run-Time Migration Guide Release 1.1, SC26-3118 for assistance with your migration to Language Environment.

For a comparison of VSE PL/I and MVS PL/I language elements, see the publication entitled Developing Portable VSE Applications, GC33-6367.

15.1 Functional Differences

15.1.1 EGCS (VSE) to DBCS (OS Version 2) Comments

The following information is provided to those PL/I users who are currently using DOS PL/I Optimizing Compiler′s Extended Graphic Character Set (EGCS) support. The Version 1 OS PL/I compiler also has the EGCS support. The Version 2 OS PL/I compiler made enhancements to EGCS support and renamed the support, Double Byte Character Set (DBCS).

EGCS support is limited to support for the GRAPHIC string constant and GRAPHIC data type. It introduced the GRAPHIC compiler option, which allows the installation (but not the user) to define the graphic control characters. These control characters consist of the shift-in, shift-out, graphic blank, graphic quote and graphic letter ′ G′. The format of the graphic string constant (with a graphic

′G′ suffix) is fixed.

DBCS support provides for additional new function (including free-format input) over that provided with EGCS. For a comprehensive list of the DBCS support items, see OS PL/I Version 2 Language Reference, SC26-4308 and the OS PL/I Version 2 Programming Guide, SC26-4307.

VSE migrations to the OS PL/I Version 2 product, should not experience any code problems given that they didn′t modify EGCS code points; that is, upward compatibility is provided.

333 OS/390 specifications

IBM OS/390, a versatile operating system, was a cornerstone in enterprise environments and played a pivotal role in mainframe computing. Released in the mid-1990s, OS/390 combined the strengths of IBM's MVS (Multiple Virtual Storage) with new features and enhancements, targeting scalability, reliability, and performance in demanding business applications.

One of the key features of OS/390 was its robust support for multiple users and processes. The system allowed thousands of concurrent users to access applications and data, ensuring high availability and minimizing downtime—a critical requirement for many large organizations. This scalability was supported through various enhancements in memory management and processor scheduling, enabling optimal resource allocation across diverse workloads.

OS/390 was known for its superior workload management capabilities. The Workload Manager (WLM) component allowed administrators to define service policies, specifying how system resources would be allocated according to the priority of tasks. This ensured that critical business processes received the necessary resources while less critical tasks were managed more flexibly.

Another significant characteristic of OS/390 was its commitment to security. The operating system provided comprehensive security features, including user authentication, data encryption, and auditing capabilities. This focus on security was vital for organizations handling sensitive data, ensuring compliance with regulations and safeguarding against unauthorized access.

OS/390 also supported advanced technologies that facilitated integration and development. The system included features like the IBM CICS (Customer Information Control System) for transaction processing and IMS (Information Management System) for database management. These technologies allowed organizations to build robust, high-performance applications tailored to specific business needs.

The ease of network integration was another strength of OS/390. With the advent of the Internet and global connectivity, OS/390 systems could easily interface with various network protocols, enabling businesses to operate in a connected world. This inclusion paved the way for many organizations to expand their capabilities and offer new services, driving digital transformation.

In conclusion, IBM OS/390 represented a significant advancement in mainframe technology, combining scalability, security, and robust workload management. Its rich feature set and support for critical enterprise applications solidified its role as a vital component of many organizations' IT infrastructures, ensuring they could meet their operational challenges head-on while supporting future growth. As technology continues to evolve, the legacy of OS/390 remains influential in the realm of computing.

IBM OS/390 manual Pl/I, 333

Models: OS/390

Chapter 15. PL/I

© Copyright IBM Corp. 1998

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OS/390 specifications