CalABC is not just a simple virtual calculator but an equation solver. That is, it's designed to solve an entire equation consisting of a series of numbers and mathematical signs only when you tap the equal button instead of making a calculation every time you tap a sign like + and . In this way, you can go back with the backspace button to correct a mistake when necessary.
There is nothing difficult about how to use CalABC. The only aspect where you have to be careful is that you must not end with a mathematical sign or one of the parentheses when you are ready to make a calculation. Or the equal pad will remain disabled. (See Screenshot 201.) In such event, you can use the backspace button to remove the last mathematical sign or continue to enter one or more numbers. Then the equal pad will come back active. (See Screenshot 202.)
As you see on the main application screen, there are four buttons on the navigation bar at the bottom. (See Screenshot 203.) Use the Clear button to clear the equation path. You already know what the backspace button does. Tap it to remove the last number or mathematical sign on the equation path. There are two buttons that are named alike. When you tap Copy 1, CalABC will copy the number shown on the answer display into the clipboard. Similarly, use Copy 2 to copy the equation on the equation path into the clipboard.
3. Math signs (inapp purchase) When you purchase Math signs, you will have access to more mathematical signs on top of simple ones like +, , x. Returning to the main application screen, you will find three additional buttons on the navigation bar at the bottom. As you see in Screenshot 301, these additional math buttons may be disabled. That's because the equation path has ended with a number. Imagine a situation where you want to enter the π value by tapping the π button. Suppose that the last number you have on the equation path is 44444.666. If you appended 3.14159 to the equation, you would have 44444.6663.14159, which doesn't make sense mathematically, right? That's why CalABC will automatically disable the math buttons when the equation has ended with a number. Now, as shown in Screenshot 302, if the equation ends with a mathematical sign, those buttons will become active.
So there are three additional buttons at the bottom. Tapping the π button, you can append the π value to the equation. 3.14? Well, you decide. You can control the position of the decimal place in Preferences. The default value is 3.14. Similary, tap the e button to append the value (2.718281828) of the base of the natural logarithm to the equation. For now, this value is fixed.
There is one more button we haven't discussed. When you tap the math signs button, a popover list will deploy. (See Screenshot 303.) And you will have access to 9 mathematical notations.
When you select a math sign, you will be prompted to enter one or more numbers. For example, if you select y to the power x on the popover list, you will be prompted to enter two values. (See Screenshot 304.) The first entry refers to 7 while the other refers to x. When you enter values and then tap Continue, CalABC will create a mathematical notation, which will be inserted to the equation path. (See Screenshot 305.)
4. Answer list (inapp purchase) The purchase of Answer list will give you access to the Answers list, which appears to the left of the virtual calculator. Every time you make a calculation by tapping the equal pad, CalABC will insert the answer to the list. When you select an answer on the list, the application will automatically copy the text value to the clipboard. A status message will appear briefly at the bottom of the virtual calculator. (See Screenshot 401.) Furthermore, depending on how you configure settings in Preferences, you can let CalABC append the answer of your selection to the equation path.
If you want to delete any of the answers from the list, first, tap the Delete button on the navigation bar at the bottom. Then each answer will be preceeded by a small red symbol. (See Screenshot 402.) Now, tap the symbol to the left of the answer you want to delete. And the red Delete button will appear to the right. When you tap this button, CalABC will delete the answer of your selection without prompting you for confirmation. When you finish deleting answers, tap the Delete button on the navigation bar again. And all delete symbols will go away.
If you want to eradicate all answers in the list, tap the Delete all button on the navigation bar at the bottom. By default, you will be prompted for confirmation. (See Screenshot 403.) If you choose Yes, the list will be cleared.
