Changing number mode changes the calculator display, but any data stored in the calculator is retained. Therefore you can convert between different number systems by entering data and then selecting the new number base. However, only the decimal system has a decimal point, the other number bases work for integers only. Also note that a number in one system will require a larger number of digits in a lower number base, which may cause an overflow. This is especially likely when converting to binary.

When converting between different number modes it is sometimes inconvenient to keep going to the Mode dialogue. For quick Number Mode changes, either use the quick mode buttons on the fifth row of the function keypad, or use the accelerator or shortcut keys. These are all obtained by holding down Shift and Alt on the keyboard and typing the appropriate letter, i.e. D for Decimal, H for Hexadecimal, T for Time, etc. See the listing of keyboard accelerators.

There is a fifth row of function keys which allow you to quickly switch
between modes. This is especially useful when working in multiple
number bases. The fifth function keypad row is enabled by default
when the software is installed but can be removed using the View
tab of the options dialogue. **Note that earlier versions used four
rows of function keys and this will be picked up as the default, so you
may need to explicitly set the number of rows
to five**.

Beyond base 16 it is not practical to provide buttons for letters, and the computer keyboard must be used. The convention is for the upper case letter to be used (i.e. shifted letter).

An interesting example is base 36, where all the decimal digits and all the letters of the alphabet are available. In this case, words can be encoded and made the subject of computation. This gives interesting possibilities for word games and simple ciphers.

Example:

GADGET - 3ZS45L = CALC98

Convert to Decimal:

743385932

Scientific calculators use algebraic precedence where multiplication and division take priority over addition and subtraction, regardless of the order in which the expression is presented. In this case "1 + 2 * 3" evaluates to 7, because "2*3" is evaluated first, and the result added to 1. This is the default precedence for Calc98.

The single level of built-in algebraic precedence may not be sufficient for more complex expressions, and the solution is to use parentheses.

Users of RPN (Reverse Polish Notation) calculators are able to perform complex calculations without parentheses because each value can be pushed onto a "stack" and the operators applied in order. This elegant method was available in early Hewlett-Packard scientific models before calculators with parentheses became available. Many of the users of these calculators prefer to continue using RPN, so this has been added as a third precedence option.

In RPN mode some of the button legends and
behaviour change. In particular, the **=** button is labelled **Enter**
and is used to enter or push a value onto the stack. The **Min** and
**MR**
buttons become **STO** and **RCL** respectively. There are no parenthesis
buttons, but **CLx** and **REG** buttons are provided.