:Prompt Var1[, Var2, ..., VarN]
Will prompt the user to enter information to store into a variable by displaying the variable and a question mark. It works similarly to Input.
This program asks the user to enter a value for A and B, then adds them, and displays the sum. If the user inputs 3 for A and 4 for B, the screen would end up looking like:
A? 3 B? 4 7