Editing Action! (programming language) (section)

==Development environment==
Action! is one of the earlier examples of the OSS SuperCartridge format. Although ROM cartridges for the Atari could support 16&nbsp;kB,<ref>{{cite book |last=Chadwick |first=Ian |date=1983 |title=Mapping the Atari |url=https://archive.org/details/Mapping_the_Atari/page/n133/mode/1up |publisher=[[Compute!]] |page=103 |isbn=9780874550047}}</ref> OSS opted for bank-switching 16&nbsp;kB, organized as four 4&nbsp;kB blocks, [[Memory map|mapped]] onto 8kB of [[address space]]. The lower 4&nbsp;kB did not change, and system could [[bank switch]] between the other three blocks by changing the value in address $AFFF.<ref>{{cite web |url=https://atariwiki.org/wiki/Wiki.jsp?page=Cartridges |title= RAM/ROM Control On An XL/XE Computer |website=AtariWiki}}</ref>{{sfn|Moriarty|1984|p=55}} This allowed for more [[RAM]] available for user programs.<ref>{{cite web |url=https://atariwiki.org/wiki/attach/Newsletters/OSS_Newsletter-Summer_1983.pdf |title=OSS Newsletter |author=<!--Not stated--> |date=1983 |website=atariwiki.org |access-date=2024-05-24}}</ref>

Action! used this design by breaking the system into four sections, the editor, the compiler, a [[machine code monitor|monitor]] for testing code and switching between the editor and compiler, and the run-time library.{{sfn|Moriarty|1984|p=55}} The run-time library is stored in the cartridge itself. To distribute standalone applications requires a separate run-time package which was sold by OSS as the Action! Toolkit.{{sfn|Moriarty|1984}}

Action! constructs were designed to map cleanly to 6502 [[opcode]]s, to provide high performance without needing complex optimizations in the [[one-pass compiler]].<ref>[http://atariki.krap.pl/index.php/ACTION! ACTION! in Atariki (PL)]</ref> For example, local variables are assigned fixed addresses in memory, instead of being allocated on a stack of [[activation record]]s. This eliminates the significant overhead associated with stack management, which is especially difficult in the case of the 6502's 256-byte stack. However, this precludes the use of [[recursion]].{{sfn|Moriarty|1984}}

Unlike the integrated [[Atari BASIC]] and [[Atari Assembler Editor]] environments, the Action! editor does not use line numbers. It has a fullscreen, scrolling display capable of displaying two windows, and includes block operations and global search and replace.{{sfn|Moriarty|1984}}

The monitor serves as a debugger, allowing an entire program or individual functions to be run, memory to be displayed and modified, and program execution to be traced.{{sfn|Moriarty|1984}}