How to Use rpCalc



If you know how to use an RPN calculator (like some Hewlett-Packard models), you know how to use rpCalc. It stores previous results in four registers (usually labeled X, Y, Z and T), and the numbers are entered before the operators.

The quickest way to enter numbers and the four basic operators is to use the number pad on the keyboard. For the other keys, the name on the key can be typed (not case-sensitive). What has been typed shows in the box below the keys. The tab key may be used to automatically complete a partially typed command. Of course, the mouse may also be used to hit any key.

A few keys have unusual labels to allow them to be typed: "RCIP" is 1/X, "tn^X" is 10^X, "R<" rolls the stack back (or down), "R>" rolls the stack forward (or up), "x<>y" is exchange, "CLR" clears the registers, and "<-" is backspace.

A few commands ("STO", "RCL" and "PLCS") prompt for a number from zero through nine. This number will be the memory register number or the number of decimal places for the display.

Information Windows

A menu can be displayed by hitting the Esc key or by clicking on the main number (LCD) display with the right mouse button. This menu includes commands to display a list of registers, a calculation history list, and a memory contents list. These commands will show a new window with the requested information. The extra window is tabbed to toggle between the three lists. Buttons on the window can be used to copy the numbers to the calculator (X-register) or to the clipboard (with buttons to copy either all decimal places or the formatted fixed decimal place number).

The register list shows the current contents of each register (X, Y, Z and T). The numbers are shown to full precision, with all available decimal places shown.

The history list shows algebraic equations for every calculation that was done in the current rpCalc session. The numbers are shown to the same precision as the main display.

The memory list shows the current contents of the ten memory registers (0-9). The numbers are shown to the same precision as the main display.

Alternate Bases

An alternate base window can be shown from the display context menu (right-click the LCD or hit the Esc key). This window shows the hexadecimal, octal and binary equivalents of the number in the X-register, rounded to the nearest integer.

The Hex, Octal, Binary and Decimal buttons are used to change the input mode to that base. There are also keyboard shortcuts (Alt-x, Alt-o, Alt-b and Alt-d) that do the same thing. Any typed number is then interpreted using the current base. The current mode is kept until the user changes it.

Prefixes consisting of a zero followed by the base code (x, o, b or d) can be used to temporarily change the input mode. For example, "0x56c" enters the hex number 56c (1388 in decimal). The input mode goes back to decimal after hitting enter or using a function. Note that the alternate base window must be displayed for these prefixes to function.

When using non-decimal input modes, the decimal equivalent of the entry is still displayed on the main LCD. Also, when in hex input mode, commands beginning with letters A-F can only be typed if a colon (":") is used as a command prefix.

There is also a Copy Value button that copies the value of the current input mode base to the clipboard for use in other applications.

The option dialog has a setting for a limit on the number of bits. Numbers larger than the limit will display "overflow" in the alternate base window. There is also a setting to show negative numbers as a two's complement number.


The OPT key will show an options dialog box. This includes settings for startup conditions, display parameters, angle units, alternate bases and extra views.

The startup options include whether to save the register entries between sessions and whether to open the extra data or alternate base windows when starting rpCalc.

The display options include several number formatting settings. The number of decimal places, use of space as a thousands separator and various exponent and engineering notation (exponents divisible by three) options can be set. There are also settings for viewing all four RPN registers on the main display and for hiding the LCD highlight (clearer for some resolution and window size settings).

The extra views section includes buttons for showing the extra data window, the alternate base window, and this readme file. The number of saved equations in the history list can also be set.