' Convert ounces to pounds
PRINT "Enter number of ounces" 
INPUT OUNCES
PRINT "Number of pounds:", OUNCES / 16
END

Mistakes in Typing Data

When an INPUT statement asks for a number, it will reject an unacceptable number and ask that you type it again. This can get confusing unless you look carefully at what happens. Say that the above program is run and that the INPUT statement has asked for a number. The user has typed "rats" but has not yet hit enter.

Enter number of ounces
? rats

"rats" is not acceptable when INPUT expects a number. When the user hits enter, the following will appear:

Enter number of ounces
? rats

Redo from start
? _

The INPUT statement did not accept "rats" and so writes the prompt "Redo from start" and then writes the "?" as usual. Notice that the program is "stuck" on the INPUT statement. It won't do the PRINT statement (or any other) again, so you won't see the "Enter number of ounces" prompt again. Now say that the user enters an acceptable value:

Enter number of ounces
? rats

Redo from start
? 12
Number of pounds       .75

Once the INPUT statement gets an acceptable number, it continues as usual by putting the number in the variable. The rest of the program executes as usual.

An "acceptable number" means something you typed that looks like a number. The number might be incorrect data. The INPUT statement does not know when it is given incorrect data.

' Convert ounces to pounds
PRINT "Enter number of ounces" 
INPUT OUNCES
PRINT "Number of pounds:", OUNCES / 16
END

Enter number of ounces
? 640