Fix scientific calculator

DEG says that the angle unit is set to degrees. You can change it to RADians, or GRADs. However much you want to get rid of all of them you will always have one of them. Learn to live with them.
FIX says that the decimal displays will always show a fixed number of decimals. You can decide how many you keep. Apparently your calculator is configured not to show any decimal digits: the number of fixed digits is set to zero. Change it to some other number
There are other display formats : Engineering ENG, and Scientific (SCI)
There is another format (possibly 2) called Norm 1 or Norm 2.
Set you calculator to one of the Normal formats.
Press SHIFT MODE to enter (Setup) and configure.
Advice: Learn to use your calculator. The best way to achieve mastery is to look inside the manual whenever you do not understand something.

14! is an eleven-digit number. The only way your ten-digit calculator can display that number is to convert it to scientific notation. A twelve-digit calculator such as a TI-89 can display that number, but 23! is a 23-digit number and even a TI-89 cannot display that number.

You can set your display mode to FIX or NORMAL ( 1 or 2) if you have them. However if the result is too small ( less then 0.001) or too large the calculator will use the scientific format. Generally if there are not enough display positions to show your result, the calculator uses scientific notation.

You've got the display set to fixed decimal notation. To change it, press SHIFT MODE 7 to switch to a scientific notation or SHIFT MODE 8 and then 1 or 2 to switch to one of the norm display modes.

norm1 switches to scientific notation if the magnitude of the number is less than 0.01 .
norm2 switches to scientific notation if the magnitude of the number is less than 0.000000001 .

Press SHIFT [SETUP]. You can select FIX for fixed-decimal or NORM for normal display. For FIX the calculator will prompt for the number of digits. NORM gives you two choices: 1 will display numbers of magnitude less than 10E-2 in scientific notation, 2 won't switch to scientific notation until the magnitude drops below 10E-9.

I am not sure what you want because the mathIO mode IS THE ONE THAT DISPLAYS results as fractions.
You have two display modes: MthIO (with fractions, radicals) and LineIO (with decimals). Which one do you want?
To set MthIO press [Shift][MODE][1:MthIO]
To set LineIO, press [SHIFT][MODE][2:LineIO]

Concerning the scientific display mode.
Decimal numbers can be displayed in various formats, Fixed,Scientific, and Normal. If you do not want scientific display of results, just set the mode to Fix(ed) and specify the number of decimal digits. However if a number to be displayed (a result) is too small or too large IT WILL BE DISPLAYED in scientific format regardless of the mode you selected.

Press MODE, then navigate down to the display setting and select FIX and whatever number of digits you want to the right of the decimal point.

This can be done by setting the calculator to the right MODE. Press MODE 9 to turn on scientific notation. For example, compute 1 / 200 = and you will see 5 with a -03 exponent in the upper right. Press MODE 9 again and it will be displayed .005

To enter numbers in scientific notation use the EXP at the bottom. To enter .005, press 5 then EXP then +/- then 3. You will see it displayed. Then you can perform calculations with this entered number.

Check this HP FAQ:
Setting a Fixed Decimal Place You can download the manual and user guides for your calculator from here:
http://h10025.www1.hp.com/ewfrf/wc/manualCategory?lc=en&dlc=en&cc=us&product=81575&lang=en&

For more information, Faqs & how-Tosgo the HP support homepage for your calculator:
http://h10025.www1.hp.com/ewfrf/wc/product?lc=en&dlc=en&cc=us&lang=en&product=81575&

Introduction This document describes how to set the desired number of decimal places on the HP 12c calculator in standard format. It also covers how to enter a number in scientific notation. Instructions for standard format

1. Press and release .
2. Press the number key for the desired number of decimal places to be displayed to the right of the decimal point (0 through 9). The calculator displays a maximum of 10 digits.

The display will show the specified number of decimal places. The answer will be rounded to the number of digits selected. Example (standard format) If the number in the display is 14.87456320, the display will be changed as follows: Keystroke Display 14.8746 14.9 15 14.87456320 Instructions for scientific notation Use scientific notation for very large or very small numbers. Type in the mantissa. After pressing, the next numbers keyed in are exponents of 10. Press . If during an operation a result has more than 10 digits, the calculator automatically displays the number in scientific notation

Introduction This document describes how to set the desired number of decimal places on the HP 12c calculator in standard format. It also covers how to enter a number in scientific notation. Instructions for standard format

1. Press and release .
2. Press the number key for the desired number of decimal places to be displayed to the right of the decimal point (0 through 9). The calculator displays a maximum of 10 digits.

The display will show the specified number of decimal places. The answer will be rounded to the number of digits selected. Example (standard format) If the number in the display is 14.87456320, the display will be changed as follows: Keystroke Display 14.8746 14.9 15 14.87456320 Instructions for scientific notation Use scientific notation for very large or very small numbers. Type in the mantissa. After pressing, the next numbers keyed in are exponents of 10. Press . If during an operation a result has more than 10 digits, the calculator automatically displays the number in scientific notation

The FX-115ES can only handle ten digits. 14! is an eleven-digit number, thus the calculator can only display the first ten digits and a power of ten.