# Perpenso™ Calc Frequently Asked Questions

## General

Why is iOS 4.3 the minimum iOS version?

## Worksheets

How do I get to the worksheets?

## Scientific Mode

What does the button do?

Where is the rectangular coordinate to polar coordinate conversion?

How do I convert a decimal number to a fraction?

Why are polar values rounded when they are entered?

Adding or subtracting a percentage doesn't seem to work correctly?

Why can't I see numbers as dotted quads?

## Statistics Mode

Why does percentile, , differ slightly from some textbook examples?

## Business Mode

How do I perform breakeven point, profit margin, time value of money or cash flow calculations?

## Hex Mode

Why aren't there buttons to shift or rotate by one bit?

How can I get a decimal calculation to respect the current int type and size settings?

## General

Q. Why is iOS 4.3 the minimum iOS version?

A. In order to support the iPhone 5 we needed to upgrade to newer development tools. These tools require a minimum iOS versions of 4.3.

## Worksheets

Q. How do I get to the worksheets?

A. Press the info button in order to switch to the flip side view and then press the worksheets tab. To return to the calculator press the "Done" button.

## Scientific Mode

Q. What does the button do?

A. The button is a prefix that modifies the behavior of some buttons. For example the button cycles the angular mode between degrees, radians and gradians. However will cycle the mode and convert the currently displayed number to the new unit of measurement.

Q. Where is the rectangular coordinate to polar coordinate conversion?

A. There is no explicit coordinate conversion because complex numbers provide the same functionality. Enter your coordinate as a cartesian (rectangular) or polar complex number and use the and buttons to convert. For example create a complex number in cartesian form by entering the x value, pressing , entering the y value and then press to convert to polar form. Or create a complex number in polar form by entering the length, pressing , entering the angle and then press to convert to cartesian form.

Q. How do I enter fractions?

A. Use two decimal points. One decimal point between the integer part of the number and the fractional numerator and another decimal point between the fractional numerator and denominator. For example enter 1.2.3 for one and two-thirds and .3.4 for three-fourths.

Q. How do I convert a decimal number to a fraction?

A. The button converts a decimal number to a fraction. Some numbers cannot be accurately converted to a fraction and will remain decimal numbers. If a fraction is currently displayed then toggles between proper and improper forms. Use to convert a fraction to a decimal number. For example 1.625 yields 13/8. Pressing a second time yields 1 5/8. Following this with yields 1.625.

Q. Why are polar values rounded when they are entered?

A. Internally complex numbers are stored in a cartesian representation. The perceived rounding is a result of the conversion between cartesian and polar representations.

Q. Adding or subtracting a percentage doesn't seem to work correctly?

A. You may be encountering a common calculator special case. If there is an immediately pending addition or subtraction operation then the normally computed percentage is multiplied by the initial term of the addition or subtraction. This calculates the percentage rise or percentage fall of the initial term. For example 120 + 10% has a calculated percentage rise of 12 and an overall result of 132 (120 + 12).

Q. Why can't I see numbers as dotted quads?

A. Normally dotted quad notation is only being used for numeric entry and not for general use. Values entered as dotted quads are displayed as their equivalent decimal values. In the optional hex mode the dotted quad representation of a value may be displayed.

## Statistics Mode

Q. Why does percentile, , differ slightly from some textbook examples?

A. There is no standard definition of percentile. The U.S. National Institute of Standards and Technology offers calculations that are commonly used in software applications such as spreadsheets and in textbooks. By default Perpenso Calc uses the spreadsheet style calculation but textbook style is also available via the prefix. If you wish to compare results to your spreadsheet keep in mind that Perpenso Calc expects k in the range 0 to 100 but spreadsheets usually expect an alpha value in the range 0.0 to 1.0.

## Business Mode

Q. How do I perform breakeven point, profit margin, time value of money or cash flow calculations?

A. In general these calculations are performed by setting a series of variables and then indicating another variable to be calculated using these settings. For example in Time Value of Money (TVM) calculations there are five key variables: number of payment periods, interest per year, present value, periodic payment and future value. Set any four of these variables and the fifth may be calculated. There are also a few prerequisite variables that must be set appropriately: payments per year, interest compoundings per year and payment timing (beginning or end of period). These calculations may be performed using the traditional button based interface or the worksheets.

For example: You have secured a 5 year loan at 6% and you can afford a monthly payment of 400, what is the maximum that you can borrow (aka the present value)?

If the mode annunciator shows "BEG" then switch to the end of period mode by pressing .

The present value is 20,690.22.

## Hex Mode

Q. Why aren't there buttons to shift or rotate by one bit?

A. The rotate and shift operations normally require a second operand, the number of bits to shift. However the prefix can be used to do an immediate one bit shift or rotate. For example 4 yields 8.

Q. How can I get a decimal calculation to respect the current int type and size settings?

A. Decimal operations are always performed with 20 decimal digits regardless of whether you are in hex mode or not. Hex, octal and binary calculations are always done in accordance with the int type (signed or unsigned) and size (64-bit or 32-bit) settings. However a decimal number can be reinterpreted using the current int type and size settings with . So the answer is to perform a normal decimal operation using and then convert the result using . If the current setting is unsigned 32-bit then decimal yields -1 and will reinterpret -1 to yield 4294967295. Which is hex FFFFFFFF. Note that hex directly yields FFFFFFFF.