Editing RPL (programming language) (section)

{{Short description|Handheld calculator operating system}}
{{About||the programming language for the Commodore PET/CBM computers|Reverse Polish Language|the compiled database programming language|Real-time Programming Language}}
{{Use dmy dates|date=April 2019|cs1-dates=y}}
{{Use list-defined references|date=October 2023}}

{{Infobox programming language
| name = RPL
| logo =
| paradigm = [[Concatenative programming|Concatenative]] ([[stack-oriented programming language|stack-based]]),<ref name="Joy_2020"/> [[structured programming|structured]]
| year = 1984<!-- development start --> (1986<!-- first products using it -->)
| designer = [[Hewlett-Packard]]
| developer =
| latest_release_version = <!-- X.Y.Z/{{release date|df=yes|YYYY|MM|DD}} -->
| latest_release_date = 2012-04-26<!-- HP 50g 2.16 --><ref name="HP_4"/><ref name="HP_7"/><ref name="HP_5"/><ref name="HP_6"/>
| discontinued = 2015<!-- HP 50g -->
| typing =
| implementations =
| dialects = System RPL, User RPL
| influenced_by = [[Reverse Polish Notation|RPN]], [[Forth (programming language)|Forth]], [[Lisp (programming language)|Lisp]]<ref name="HPJ38"/>
| influenced =
| operating_system = [[Hewlett-Packard|HP]] [[calculator]]s
| license =
| website =
| file_ext =
}}
[[File:HP48G.jpg | thumb | 220x124px | right | HP 48G calculator, uses RPL ]]

'''RPL'''{{ref|rpl_acronym_note_1}} is a [[calculator|handheld calculator]] operating system and application [[programming language]] used on [[Hewlett-Packard]]'s scientific graphing [[Reverse Polish Notation|RPN]] (Reverse Polish Notation) calculators of the [[HP-28 series|HP 28]], [[HP 48 series|48]], [[HP 49 series|49]] and [[HP 50g|50]] series, but it is also usable on non-RPN calculators, such as the [[HP 38G|38]], [[HP 39/40 series|39 and 40]] series. Internally, it was also utilized by the [[HP-17B|17B]], [[HP-18C|18C]], [[HP-19B|19B]] and [[HP-27S|27S]].<ref name="RPLMAN"/>

RPL is a [[structured programming]] language based on RPN, but equally capable of processing [[infix notation|algebraic]] expressions and formulae, implemented as a [[threaded code|threaded interpreter]].<ref name="RPL3"/> RPL has many similarities to [[Forth (programming language)|Forth]], both languages being [[stack-oriented programming language|stack]]-based, as well as the list-based [[LISP]]. Contrary to previous HP RPN calculators, which had a fixed [[4-level RPN|four-level stack]], the [[dynamic RPN stack|dynamic stack]] used by RPL is only limited by available [[random-access memory|RAM]], with the calculator displaying an error message when running out of memory rather than silently dropping arguments off the stack as in fixed-sized RPN stacks.<ref name="Wessman_2016"/>

RPL originated from HP's [[Corvallis, Oregon]] development facility in 1984 as a replacement for the previous practice of implementing the [[operating systems]] of calculators in [[assembly language]].<ref name="RPLMAN"/> The first calculator utilizing it internally was the HP-18C and the first calculator making it available to users was the HP-28C, both from 1986.<ref name="Wickes_1987"/><ref name="RPLMAN"/> The last pocket calculator supporting RPL, the HP 50g, was discontinued in 2015.<ref name="Kuperus_2015_1"/><ref name="Kuperus_2015_2"/><ref name="Wessman_2015"/>  However,<!-- an [[Mobile app|app]] is available for [[Android (operating system)|Android]], go49gp[https://play.google.com/store/apps/details?id=o2s.emul.hp49gp&hl=en_US], which emulates the HP 49g+/50g and will run RPL programs. --> multiple emulators that can emulate HP's RPL calculators exist that run on a range of operating systems, and devices, including iOS and Android smartphones. {{anchor|newRPL|DB48X}}There are also a number of community projects to recreate and extend RPL on newer calculators, like [[newRPL]]<ref name="Lapilli_2014_1"/><ref name="Lapilli_2021"/> or [[DB48X]],<ref name="deDinechin_2022"/><ref name="deDinechin_2023"/> which may add features or improve performance.<ref name="Lapilli_2014_2"/>