1. Text-to-speech voice function You can prevent mistakes by hearing the voice 2. Undo function Each time you press the back space button, you can go back to the past input. You can also go back to past inputs after the calculation, so we can respond flexibly to typing mistakes. 3. Mutilingual - number format It corresponds to the difference in the digital format of each country. (example) 1,234,567.89 Japan 1 234 567,89 France 1.234.567,89 Germany 1'234'567.89 Switzerland 4. Mutilingual - speech This application uses Google's TextToSpeech (TTS) feature, so it can use multiple languages.