HP 20B - Manual (Page 15)

Basic Features
15
In this manual, diagrams called Menu Maps are included at the beginning of each section to assist you with navigating
through the menus used for that section. For an example of a menu map, see Figure 7.
Figure 7 The Menu Map for the Break-even Menu
There are four types of menu items:
1. Read/write. Read/write menu items, such as Fixed in the Break-even menu shown above, are easily recognizable,
because when they are selected, both the INPUT and small (=) annunciators are lit. When lit, these annunciators
indicate that entering a number and pressing
I
will store the entered number in the displayed menu item.
Pressing
=
(outside of a mathematical operation) calculates the value for that item based on available data.
2. Read-only. Read-only items such as Internal Rate of Return ( IRR% ) in the IRR menu are display-only; they are
calculated values computed internally by the calculator.
3. Write-only. Write-only items, such as investment interest rate ( Inv. I% ) in the Net Present Value (NPV) menu, are
similar to read/write items in that the INPUT annunciator is lit when these items are selected, indicating that entering a
number and pressing
I
stores that number in that menu item. However, the
=
key does not calculate a
value for that item.
4. Special items. Special items, such as the Degree/Radian option in the Mode menu, the items of the Reset menu, and
the items of the Percent Calculation (%calc ) menu perform an action when
I
is pressed. Depending on the
menu, this action can be the selection of a sub-menu (%calc menu), changing a mode or setting (Mode menu), or
erasing data (Reset menu).