When you type a number, such as “123”, computers convert the text values of “123” into an internal representation used by the computer. There are many possible ways that numbers can be represented inside a computer. For example, the computer could:
- keep numbers in their original text format “123” (decimal format)
- convert them into a binary representation (binary integers)
- a “floating point” representation (floating point or “float” format)
- or even a “binary coded decimal” (BCD) representation.
Each internal format has benefits and drawbacks, depending on the application. Most computers (and programming systems) convert entered numbers from their original text format into either integer format or floating-point number format.
App Inventor converts values to floating point format. Which is fine, except that you will encounter some odd and subtle issues. As the link below notes, in App Inventor arithmetic, 0.3 + 0.6 does not equal 0.9!