== Introduction ==
<b>RSX</b> (<b>R</b>esident <b>S</b>ystem e<b>X</b>tensions) were a way to extend the command set of Locomotive BASIC, e.g. for accessing external peripherals like disk drives, light pens, speech synthesizers and so on.
RSX command extensions can be implemented through ROMs (like AMSDOS or other disk operating systems) or by programs.
== Reference documentation ==
Reference documentation to write a RSX (assembly-level calls to register one, etc) is supplied in [[Soft968: CPC 464/664/6128 Firmware]] section 10.
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