Characters In, Characters Out

The data a keyboard sends to a program is character data, even when the characters include the digits '0' through '9'.

If your program does arithmetic, the input characters will be converted into one of the primitive numeric types. Then the result is calculated (using arithmetic), and then the result is converted to character data. The information a program sends to the monitor is character data:

(Actually, the characters are not really sent directly to the monitor. They, along with everything else the monitor displays, are first converted into a video signal by a graphics card. This business of converting data from one form to another is very common in computers.)