Preserving DM42 muscle memory

A lot of effort went into preserving DM42/HP42 muscle memory for DB48X. This makes it possible (at least to me) to use DB48X without any overlay, although having a keyboard overlay is preferable.

Changes to primary keyboard features

1. ∑+/∑- replaced with ⚙ (automatic menu based on stack content) and BackMenu
2. e^x and LOG swapped. This is really because math tends to use e^x way more often than decimal log.
3. XEQ, which does not exist on HP48, replaced with '(), which I memorize as "eXpression/EQuation", and GTO replaced with Loop for the LoopMenu (which has no GTO, although this is probably coming some day)
4. RCL replaced with VAR for the VariablesMenu, which plays a similar role (so easy to memorize)
5. % replaced with FRAC for the FractionsMenu, which does include %. Also easy to memorize I hope
6. R↓ replaced with STK for StackMenu, which does include all sorts of stack manipulation operations
7. 𝛑 replaced with CONST for the ConstantsMenu, which does include 𝛑 and other constants
8. LastX replaced with Last for LastArguments
9. CLEAR replaced with CLR for the ClearThingsMenu which includes the Clear stack command
10. ASN replaced with ->Num (to memorise, ASN = As Numerical Value).
11. Up and down arrows replaced with left and right

Commands that are in the same spot

Most other commands are literally at the same spot, sometimes invoking a menu instead of a command: 1/x, y^x, √x, x^2, 10^x, LN, STO, COMPLEX (ComplexMenu), sin, cos, tan and their inverse, ENTER (duh), X⇆Y (Swap in RPL), +/- (Negate in RPL), EEX, Backspace / Drop, Alpha, Modes, Disp, Solver, Integration, Matrix, Statistics, Bases, Conversions, Flags, Probabilities, User mode (RPL equivalent of Custom, not implemented yet), PGM.FN for ProgramMenu, Print, Setup, Show, R/S (Evaluate or = or space in RPL), PRGM to insert RPL programs, and the Catalog.

Also, the shift key, EXIT/On, Off, and obviously +, -, * and / are all where expected. This is not a given, WP43 moved even these.

Secondary commands

There are additional secondary commands that you get through a double shift. I tried hard to make them also relatively easy to memorize:

• y√x aka xroot next to y^x,
• PolynomialsMenu menu next to x^2,
• ExpLogMenu next to 10^x,
• PartsMenu next to log (my way to memorize that is that the decimal log extracts the exponent, which is a part of the number),
• EquationsMenu next to the XEQ expression/equation key,
• MemMenu next to STO because this deals with memory,
• LibsMenu next to VAR because this deals with added objects to customize the calculator,
• MathMenu next to constants / 𝛑,
• HyperbolicMenu, CircularMenu and RealMenu menus above SIN, COS and TAN (I remember this with 'Cos' and 'Circular' beginning with C),
• "Text" next to Alpha because that's entering text in both cases,
• Undo next to Last,
• Objects next to Modes (this one I memorize by thinking these are two "general transformation" menus),
• Plot next to Disp,
• Up (up one directory) next to Backspace,
• SYMB (SymbolicMenu) next to Solver (numerical vs. symbolic equation resolution),
• Differentiation next to Integration,
• MatrixMenu next to matrix entry,
• FinancesMenu next to Stats,
• Text operations next to Base (I memorize this with "base" allowing letters in numbers),
• Units and Unit conversions where DM42 has "Convert",
• Time next to Flags (as in "flag this"),
• Number operations next to probabilities,
• Debugging next to ASN (because "asinine", OK, this one is weak),
• CharactersMenu next to Custom, because localization is a form of custom,
• Tests next to Prog because it's a subset of programming,
• I/O next to Print because printing is a special case of I/O,
• File next to Setup because both access the Flash storage,
• Graph next to Show because they both deal with graphic representations,
• {List} next to Programs because they are almost "the same thing"… in RPL,
• and finally, "Help" next to catalog, because both cover all the features of the calculator.