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FAQ - My Casio Calculator Won't Turn On | CASIO

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Frequently Asked Questions


My calculator displays answers as a fraction. How can I change it to display a decimal answer?

When the calculator solves for the expression, press the [S-D] button. The Standard-to-Decimal button will toggle a solution between a fractional and decimal answer. For example, if the solution is 1/2, this function will change the solution to 0.5. If your solution is 3/2, you can also change the solution to a mixed number by pressing [SHIFT]+[S-D], which returns 1 and 1/2.

My answer has a root symbol in it. How can I get an exact number as the answer?

For Graphing Calculators: Enter Set Up by pressing [SHIFT]+[MENU]. Change Input/Output from Math to Mth/Mix by pressing [F3] (M/M) in the on-screen function menu. Press [EXIT] and all irrational solutions will now display as decimal answers.

For the 115ES Plus 2 and 991EX: Enter Setup by pressing [SHIFT]+[MODE]. Select MthIO by pressing [1]. Select LineO (or MathI/DecimalO for the fx-991EX) by pressing [2].

Why do I keep getting an error message when I try to perform a calculation?

The type of error message you receive should broadly indicate the nature of the problem. We've provided some common messages below; for more specific information, please consult your calculator's user guide.

  • Ma ERROR / Math ERROR: The calculated result is outside of the allowable calculation range, or the expression supplied is an illegal mathematical operation (such as division by zero). Check your input values and adjust them to allow the calculation result to be within the allowable range. If you are using memory for your calculation, make sure that you check the memory value.
  • Syn ERROR / Syntax ERROR: The supplied expression is formatted in a way that the calculator can not understand. Check your expression and revise it if necessary. Some of our calculators will allow you to jump to the erroneous syntax in the expression by pressing [>] (Goto).
  • Stk ERROR / Stack ERROR: The performed calculation has caused the capacity of the numeric stack or the command stack to be exceeded. Simply put: the calculator has too much to do. Simplify your expression, or split the expression into two or more parts, then execute the parts separately.
  • Mem ERROR: The calculator executed a matrix, graphing, or some other operation that caused remaining memory capacity to be exceeded. To correct this, delete data stored in memory that is no longer needed. Make sure that the number of variables used in your expression does not exceed the number of variables that are available.

Other error messages may appear to let you know that a calculation you are trying to perform is not compatible with your current mode, angle unit, display, or other setting. If this happens, please check the Setup menu of your calculator and try again.

I accidentally deleted my Add-in icons. How do I get them back?

If you accidentally erased the Geometry, Picture Plot, Conversion or Python Add-In icons, reset the calculator's Setup Data and/or the Main Memory. Please consult your calculator's specific user guide on how to perform this feature from the SYSTEM settings. If you accidentally erased the Add-Ins and Storage, you will need to visit the Casio Worldwide Education website at to download the Add-In software and image library. Connect the calculator to the computer with the supplied USB cable, then follow the instructions at the website to finish the re-installation process.

My calculator won't turn on or is frozen.

Does not turn on: Replace the batteries in the device with charged batteries. Check to make sure the batteries are in the correct polar position. If the calculator still fails to turn on, depress the restart button for five seconds on the back of the calculator with the end of a paperclip or similar. If the calculator still fails to turn on, try connecting the unit to your PC using the supplied USB cable. Please contact Casio Support if the problem persists.

Is frozen or stuck in an infinite loop: Tap the [AC] button repeatedly until the program or calculation terminates. If the calculator is not detecting the [AC] command, depress the restart button for five seconds on the back of the calculator with the end of a paperclip or similar. Optionally, remove the batteries from the device or cover the solar cell until the unit loses power. When the unit is off, resume power to the calculator and turn back on to continue normal use.

Writing programs using the physical keypad is cumbersome. Is there a faster way to write programs?

All current programmable calculators offered by Casio feature USB-to-PC connectivity. Plug your calculator into your PC and select [F1] (USB Flash) when prompted. Using Windows File Explorer, the calculator will appear as "USB Drive." Python programs are stored as PY files. You can open PY files and edit them with any text editor of your choice.

Casio BASIC files cannot be modified using a text editor.


What is Natural Textbook Display?

Natural Textbook Display is the term we use to describe how a calculator display will render and represent formulas, inputs, and fractions on the screen. Natural Textbook Display will render and represent expressions exactly as they would appear on paper or in a math book.

Calculators that feature Natural Textbook Display:

  • Graphing Calculators: fx-CG500 PRIZM CAS, fx-CG50 PRIZM, fx-9750GIII
  • Scientific Calculators: fx-55 PLUS, fx-300ES Plus 2nd Edition, fx-115ES Plus 2nd Edition, fx-991EX
  • also features Natural Textbook Display
What is an overflow error?

Whenever the integer part of a calculation result is longer than the maximum number of digits that the calculator can display, you will receive an overflow error. The result will be presented as a round number. For most of our calculators, if your solution exceeds 10^100, the calculator will provide an overflow error or a Math Error. For the fx-CG500 PRIZM CAS, solutions can't exceed 10^1000.

What is an emulator?

A calculator emulator is software that can be installed on Windows or iOS that behaves like the physical handheld device. There are many use cases for teachers and professors to use an emulator as an instructional tool. The emulator permits a user to change the size of the device, record and edit keystrokes, detach the screen from the keyboard, and much more. Emulators work great as part of a live webinar, instructional video, or interactive whiteboard for in-person learning.

Emulators are available for various Casio calculator models and they are licensed for single users or sites (classes and schools). Explore our emulators online or contact us for more details.

What is CAS?

CAS is an acronym for Computer Algebra System and is a software engine that facilitates symbolic mathematics. The core functionality of a CAS involves the manipulation of mathematical expressions in symbolic form. Presently, the fx-CG500 PRIZM CAS is the only model that natively includes a CAS.

Users of can also perform advanced mathematics with a CAS when upgrading from a free account to a paid account.

Support and Value-Adds

Do we receive credit or professional development when we attend a webinar?

You can earn a Certificate of Attendance for registering and attending more than 50% of a Casio-sponsored webinar. Contact to request your personalized copy after attending. Professional development criteria varies per state; inquire with your district's PD coordinator to find your state's policy.

Does Casio have a calculator trial or loaner program?

We do not currently offer a calculator loaner program. We can work with department leaders and district procurement professionals ad-hoc, but sample supply is limited and on a first-come-first-serve basis. Please contact us with your specific request, and we will do what we can to assist you.

What kind of support does Casio offer to educators?
  • Educator Rewards: educators, schools and districts can earn additional calculators or gift cards by purchasing multiple units for the classroom
  • Video Content: our team offers a variety of instructional and informational content through our YouTube channel, including past-webinars. Occasionally, we will offer live webinars covering instructional topics
  • Downloadables: we have a variety of downloadable content available to educators including product posters, workbooks, activities, and resource guides
  • Email Newsletter: our email newsletter empowers educators to stay current on the latest Casio offers, sales, discounts, and programs. Our newsletter is also topical for students and parents, so feel free to forward any interesting news and developments to them!
  • Tiered Pricing: educators and districts will have access to tiered pricing on select models beginning 2022. Stay tuned for more developments
Does Casio offer a content library for Python and BASIC programs?

We don't curate a library of user-generated Python or Casio BASIC programs for download; however, if this is a service you feel is valuable to you, please send us an email to let us know!

Is there an SDK for programming and software development?

There is no official software development kit for programming on Casio calculator hardware at this time.

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