(RPN) and Lisp. RPL adds the concepts of lists and functions to stack-based programming, allowing the programmer to pass unevaluated code as arguments to functions, or return unevaluated code from a function by leaving it on the stack. RPL comes in two flavors: User RPL and System RPL. User RPL is the language that a user can program directly on the calculator. System RPL requires an external compiler; this may be done on the calculator with a third-party utility, or on another machine. The two languages vary mainly in the number of low-level operations available to them. User RPL does not expose any commands that do not check their arguments. Consequently, User RPL programs cannot normally crash the calculator (and are therefore slower than System RPL programs), whereas a System RPL program that invokes a command with incorrect arguments will almost certainly leave the calculator in a state which requires a full memory reset. It is also possible to program the HP 48 directly in machine language. Emulators Emu48 for Windows Alcuin for Commodore Amiga X48 for Mac OS X, POSIX (Unix/Linux) i48 - HP48GX emulator for iOS, based on X48 m48 – HP48 emulator for the iPhone, based on Emu48 Droid48 – HP48G Emulator for Android, based on X48 droid48sx – HP48SX Emulator for Android, based on Droid48 An HP48 emulator – decompiler for Unix/Linux or Windows (using Cygwin) by Paul Courbis In popular culture A HP48 can be seen in the 2012 movie The Amazing Spider-Man and in its sequel. In the 2015 movie the Fantastic Four, an HP 48 series calculator can be seen at about 28 minutes into the film. See also Comparison of HP graphing calculators HP calculators RPL character set References Further reading (First edition: ) External links The Museum of Hewlett-Packard Calculators: HP 48S/SX The HP48 Goodies Page The HPCALC.org web site HP48 FAQ (including program list) Graphing calculators 48 Products introduced in 1990