Is the problem in the code or in the OLED screen?

[anon73444976]

@3delectro

Any suggestion on how I can make sure that the array is terminated after each character/digit that is added to the array?

By putting a terminator after each character as it is entered.

InputArray[InputArrayPos++] = charselect;
InputArray[InputArrayPos] = '\0';

(Of course, you've already ensured there's space for both...)