Control Program Facility

Control Program Facility (CPF) is the operating system of the IBM System/38.^[3] CPF represented an independendent line of development at IBM Rochester, and was unrelated to the earlier and more widely used System Support Program operating system. CPF evolved into the OS/400 operating system, which was originally known as XPF (Extended CPF).^[1]

Control Program Facility (CPF)

Developer	IBM
Written in	PL/MI[1]
Working state	Discontinued
Source model	Closed Source
Initial release	1978; 47 years ago (1978)
Latest release	Release 8 / 14 November 1986; 38 years ago (1986-11-14)[2]
Platforms	IBM System/38
Default user interface	Command-line interface
License	Proprietary
Succeeded by	OS/400

While CPF is considered to be the operating system of the System/38, much of the hardware and resource management of the platform is implemented in the System/38's Horizontal and Vertical Microcode.^[1][4]

Description of the libraries

• QGPL – general purpose library
• QSYS – system library
• QSPL – spooling library
• QTEMP – temporary library
• QSRV – system service library
• QRECOVERY – system recovery library

Data storage

In most computers prior to the System/38, and most modern ones, data stored on disk was stored in separate logical files. When data was added to a file it was written in the sector dedicated to this, or if the sector was full, on a new sector somewhere else.

The System/38 adopted the single-level store architecture, where main storage and disk storage are organized as one, from the abandoned IBM Future Systems project (FS).^[5] Every piece of data was stored separately and could be put anywhere on the system. There was no such thing as a physically contiguous file on disk, and the operating system managed the storage and recall of all data elements.

Capability-based addressing

CPF was an example of a commercially-available Capability-based operating system. System/38 was one of the few commercial computers with capability-based addressing.^[6] Capability-based addressing was removed in the follow-on OS/400 operating system.^[7]

Distributed data management

In 1986, System/38 announced support for Distributed Data Management Architecture (DDM). Such a middleware in the context of a distributed system is the software layer that lies between the operating system and applications. Distributed Data Management Architecture defines an environment for sharing data. This enables System/38 programs to create, manage, and access record-oriented files on remote System/36, System/38, and IBM mainframe systems running CICS. It also allows programs on remote System/36 and System/38 computers to create, manage, and access files of a System/38.

Programming languages

Languages supported on the System/38 included RPG III, COBOL, BASIC, and PL/I. CPF also implements the Control Language for System/38.^[8]