Registers

All arithmetic or operations are done with registers. We have 4 registers that allow us to perform these operations X, Y, Z and T. You enter a number on the display and press enter and it stores in X and the other registers are moved up.

Operations

All operations are done on the X and Y registers. So if you want to add numbers 5 and 4 you would first enter 5 and then enter 4 and then click the "OPS" button and click +. This is a visual way to enter RPN (Reverse Polish Notation).

Stack Operations

Below the display we have buttons labeled: CLST, CLx, R(down), R(Up), X<->Y, LASTX. If we want to clear out the stack completely we can use CLST to clear the stack. mind you there is no warning! CLx will clear just the X register. Each of the R buttons shift the stack up or down. and X<->Y swap the X and Y registers. If you accidentally overwrite X you can use LASTX to recall the last value in X after an operation.

Solver

The HP42S has a solver that allows you to solve for a certain variable. If you click the PRGM button that will bring up the Solver dialog. Here you can load a program from a file or enter one in the text field. Refer to the instruction manual in the Help menu button to learn the syntax. The solver dialog also has the VARMENU which allows you to store numbers in variables. You can use the RCL button on the main page to recall variables into X. Be sure to hit enter to save them in X.

File menu

On the main page there is File button that allows you to export the state of the calculator saving the registers and all variables. Then you can load the state to come back at a later time. The Help menu displays the about dialog and a link to the HP42S instructions manual.

Contact

I have loved making this project and if you have any suggestions or improvements please send me an e-mail to the following address: travis@travgm.org