Editing Execution (computing) (section)

== Runtime system ==
{{main|Runtime system}}
A ''runtime system'', also called ''runtime environment'', primarily implements portions of an [[execution model]].{{what|date=May 2020|reason=<!-- please provide reason if after this Jan-2021-update clarification is still needed -->}} This is not to be confused with the [[Run time (program lifecycle phase)|runtime]] lifecycle phase of a program, during which the runtime system is in operation. <!--Jan-2021-update begin attempting to clarify the {{what}} template-->When treating the ''runtime system'' as distinct from the ''runtime environment'' (RTE), the first may be defined as a specific part of the [[Integrated development environment|application software (IDE) used for programming]], a piece of software that provides the programmer a more convenient environment for running programs during their production ([[Software testing|testing]] and similar), while the second (RTE) would be the very [[Instance (computer science)|instance]] of an execution model being applied to the developed program which is itself then run in the aforementioned ''runtime system''.<!--hope this and previous sentence from Jan-2021-update helps (if true): "Some computer systems for security or other reasons have just the runtime environment, allowing to run just one application during the entire course of power-on cycle, so even though their algorithm might include the code of a complete operating system, such a computer - with a huge OS which is then booted in its entirety and afterwards executes this single application - such a computer system is actually without a runtime system and thus in effect performing a single program but considered having or being a runtime environment" Jan-2021-update end-->

Most [[programming language]]s have some form of runtime system that provides an environment in which programs run. This environment may address a number of issues including the [[memory management|management]] of application [[computer memory|memory]], how the program accesses [[variable (computer science)|variable]]s, mechanisms for passing parameters between [[subroutine|procedure]]s, interfacing with the [[operating system]], and otherwise. The [[compiler]] makes assumptions depending on the specific runtime system to generate correct code. Typically the runtime system will have some responsibility for setting up and managing the [[stack (abstract data type)|stack]] and [[heap (data structure)|heap]], and may include features such as [[garbage collection (computer science)|garbage collection]], [[thread (computing)|thread]]s or other [[dynamic programming language|dynamic]] features built into the language.<ref name="Aho_2007"/>