Let's consider a QBasic solution to FizzBuzz. The code works correctly, printing the required output from
1 all the way up. The problem is, since there's a lot of output, some of it scrolls off the screen. What you see when you run the program is this:
Fizz 79 Buzz Fizz 82 83 Fizz Buzz 86 Fizz 88 89 FizzBuzz 91 92 Fizz 94 Buzz Fizz 97 98 Fizz Buzz Press any key to continue
Unlike with C and its descendants, output is not a stream, but is sent directly to the screen. This means that 1) you can't scroll back in the terminal and see the previous lines,
and 2) you can't redirect output to a file to save the lines.1 Once they scroll off the screen, they're gone.
So is this a valid FizzBuzz program, if it doesn't observably display all 100 lines?
If not, does it help to add a 1-second pause or wait for user keypress after printing each line?
1 Erik the Outgolfer informs me that redirecting output to a file is possible when running QBasic in DOSBox (or in actual DOS, presumably). So that takes away the specific example I used here. I think the general question is still good to ask and might apply in some cases--for example, if
LOCATE is used, as this isn't recorded in the output buffer.