Editing IBM DPPX

{{Refimprove|date=February 2021}}
{{Infobox OS
| name                   = Distributed Processing Programming Executive (DPPX)<!-- Name of program or distribution -->
| logo                   = IBM_logo.svg
| logo caption           = 
| logo size              = 128px
| logo alt               = 
| screenshot             = <!-- filename only (no wikilink, no Image:/File:) -->
| caption                = 
| screenshot_size        = 
| screenshot_alt         = 
| collapsible            = 
| version of             = <!-- For articles about releases of operating systems ONLY -->
| developer              = [[IBM]]<!-- Name of main developer or sponsor-->
| family                 = <!-- "Unix-like" or "Microsoft Windows" -->
| working state          = Discontinued<!-- "Current", "Discontinued" (operating systems), or "No longer supported" (releases) -->
| source model           = <!-- "Open source", "Closed source", or "Shared source" -->
| released               = {{Start date and age|1978}}
| discontinued           = <!-- DON'T use this for articles about releases of operating systems -->
| RTM date               = <!-- {{Start date and age|YYYY|MM|DD|df=yes/no}} ONLY for articles about OS releases -->
| GA date                = <!-- {{Start date and age|YYYY|MM|DD|df=yes/no}} ONLY for articles about OS releases -->
| latest release version = DPPX/370
| latest release date    = {{Start date and age|1988}}
| latest preview version = 
| latest preview date    = <!-- {{Start date and age|YYYY|MM|DD|df=yes/no}} -->
| marketing target       = 
| programmed in          = [[PL/DS]]
| language               = <!-- Supported human languages (English, French, Italian, Arabic, ...) -->
| update model           = <!-- APT, Windows Update, etc. -->
| package manager        = <!-- dpkg, rpm, Windows installer, etc. -->
| supported platforms    = [[IBM 8100]], [[ES/9370]]<!-- IA-32, x64, Itanium, ARM, etc. -->
| kernel type            = <!-- Hybrid, Monolithic, Microkernel, Exokernel, Nanokernel, etc. -->
| userland               = 
| ui                     = [[Command-line interface]]
| license                = [[Proprietary software|Proprietary]]
| preceded by            = 
| succeeded by           = 
| website                = <!-- {{URL|www.example.org}} -->
| support status         = <!-- For articles about releases of operating systems ONLY -->
| other articles         = 
| prog_language          = 
}}
'''Distributed Processing Programming Executive''' is a discontinued [[operating system]] introduced by [[IBM]], pre-installed on the [[IBM 8100]] and later ported to the [[ES/9370]].

==Brief history==
* It was first introduced on the [[IBM 8100]] series, which was released in 1978.
* 1987 saw the release of Distributed Processing Programming Executive System Product (DPPX/SP) Release 4.
* In 1986, [[IBM]] decided to cease the IBM 8100 architecture to consolidate its hardware and software families.
* In 1988, they released DPPX/370 which ran on the [[ES/9370]] processors (an [[S/370]] model).<ref>{{Cite journal
|title=Porting DPPX from the IBM 8100 to the IBM ES/9370: feasibility and overview
|last=Abraham
|first=R.
|last2=Goodrich
|first2=B.F.
|journal=IBM Systems Journal
|date=March 1990
|url=http://domino.research.ibm.com/tchjr/journalindex.nsf/0/a1d0b9f8d42f592185256bfa00685c30?OpenDocument
|archive-url=https://web.archive.org/web/20060222141130/http://domino.research.ibm.com/tchjr/journalindex.nsf/0/a1d0b9f8d42f592185256bfa00685c30?OpenDocument
|archive-date=2006-02-22
|access-date=2021-02-28
|doi=10.1147/sj.291.0090
|url-access=subscription
}}</ref>
* By the end of June 1997, DPPX/370 was officially retired.

==Architecture==
{{Unreferenced section|date=February 2025}}
DPPX was written in Programming Language for Distributed Systems (PL/DS), a [[PL/I]]-derived systems programming language, similar to the [[IBM PL/S|PL/S]] systems programming language used for [[MVS]] and [[VM (operating system)|VM]]. Part of the DPPX/370 development process was developing a PL/DS 2 language, which was based on PL/DS, but with changes necessitated by the changed instruction set. (PL/DS, like PL/S, is a high-level language which encourages significant use of inline assembly.)

The user interfaces (e.g., command line) of DPPX were very clean and easy to use, the syntax of the commands, the whole concept and ideas of DPPX looked very straightforward and consistent (command line, online help, etc.), and each and every aspect was documented online and in a rich set of well organized printed manuals. A DPPX system could be operated truly operator-less and remote (hence the ''Distributed'' part of the name). One benefit of this clean design was that programs could be written in modern dialects of [[COBOL]], and dialogs could be developed interactively.

DPPX had a native DBMS with simple key-lookup architecture, and ability to move forward through a table after starting from a specific key value by issuing a read-forward command. A limitation of the DPPX DBMS was the lack of read-previous capability, which made it difficult, for example, to code page-back functionality for a screen loaded from a DPPX DBMS table. This limitation was mitigated by an enterprising young programmer (K. Riley of Anchorage, Alaska) who suggested at the application layer creating alternate keys for the DPPX tables that needed read-previous functionality. The alternate keys could then be loaded with the binary 1's complement of the primary key, at which point reading forward on the alternate key was equivalent to reading previous on the primary key.
 
==Software==
{{Unreferenced section|date=February 2025}}
In addition to the expected functions of an operating system, DPPX included several functions which allowed for remote administration, such as Distributed Host Command Facility (DHCF), which allowed a Host Command Facility (HCF) user on a mainframe to log on in either full-screen mode or line mode to execute commands as though logged on locally, and Distributed Systems Network (or Node) Executive (DSNX), which allowed a Distributed Systems Executive (DSX) (later NetView/DM) job to manage files.

Separate additional products were also available, including [[COBOL]] and [[Fortran]] compilers, the Distributed Transaction Management System (DTMS), Command Facilities Extensions (CFE), which provided easy support for full-screen applications, Data Stream Capability (DSC) to allow DPPX users to log on to applications on the mainframe, and Performance Tool (PT).

==References==
{{Reflist}}

{{IBM operating systems}}

[[Category:IBM operating systems|DPPX]]