The ESI-PD40B calculator is a basic business calculator that supports the
following operations:
                           ------------ Available from -------------
 Operation     Type        Keyboard       PushButton  OpMenu
 ---------     ----------  -----------------------------------------
 Add           Postfix     [+]            "+"         {Add}
 Subtract      Postfix     [-]            "-"         {Subtract}
 Multiply      Infix       [*]            "*"         {Multiply}
 Divide        Infix       [/]            "/"         {Divide}
 Exponent      Infix       [^]                        {Exponent}
 Percent       Function    [%]                        {Percent}
 Factorial     Function    [!]                        {Factorial}
 Reverse sign  Function    [Alt-R]        "Rev"       {Reverse sign}
 Square root   Function    [Alt-Q]                    {Square root}
 Round,2       Function    [Alt-N]                    {Round,2}
 SaveMem       Function    [>]                        {SaveMem}
 GetMem        Function    [<]                        {GetMem}
 Subtotal      Postfix     [Alt-S]        "Sub"       {Subtotal}
 Total         Terminator  [=] or [Enter] "="         {Total}
 Clear         Terminator  [Alt-L]        "Clr"       {Clear}

In addition it has a numeric keypad that contains the numerals 0 - 9 and the
decimal point.

Postfix operations operate on a number or numbers that have preceded the operator. 

Infix operations apply to the numbers immediately preceding and following the operator. Infix operations are nested, ie. they are resolved before their postfix cousins are resolved.

Functions apply only to the number currently in the input cell.

As a simple example, to add 3 - 6 = -3, enter 3 + 6 - [Enter].

For a more complex example, to calculate a bill with tax for five items: 1 coke at $1.00, three burgers at $2.00 each, and one out of a case of three apple crisps, when the case is worth $6.00, with tax altogether of 7%: enter the following keystrokes:

      1 + 2 * 3 + 6 / 3 [Alt-S] * 7 % [Enter]

When [Enter], [=], or [Alt-S] are entered without a preceding + or - operator, the + operator is assumed.

So, the above keystroke sequence is equivalent to:

  (1 + (2 * 3 = 6) + (6 / 3 = 2) = 9 + (9.00 * (7/100 = .07) = .63) = 9.63

The Paper tape would show:

      1.00 +
      2.00 *
      3.00 =
      6.00 +
      6.00 /
      3.00 =
      2.00 +
      9.00 Subtotal
      9.00 *
      7.00 % =
       .07 :
       .07 =
       .63 +
      9.63 Total

The calculator will use the previously calculated figure of the input cell if an operator is hit without entering a new number in the input cell. The input cell shows the running total of the calculation. This running total is automatically replaced by a number that you input in the input cell.

Thus 3 + + + [Enter] will give 9.00, while showing 3,6,9 after each plus, and 9 after the [Enter].

The paper tape is available for viewing and editing from the Menu, and this help text is available for viewing from the Menu.