Writing FizzBuzz in QBasic (in DOS) With Vim

This is the amalgamation of years of computering™: the pit of madness, the loss of reason. Next time they ask you to write FizzBuzz, you’ll know what to do.

Porting my Vim Setup to DOS

This tale started with a somewhat useless idea: I wanted to use part of my minimalist CLI development environment in my DOSBox setup . I already had Vim running in DOSBox, but there were some issues, like help files not being found.

As I wrote in the latter post, most of the software got into DOS by copying them, as it turned out, I had to copy some more stuff. I found a guide specifically about this here , which is very, very strange, but helpful.

So Vim was fully functional. Now I needed to customize it not via .vimrc, but _VIMRC. I think at this point copying is a recurring theme, I copied my config, but of course it didn’t work fully.

I had to say a tearful goodbye to ctags. I found a version that would run in 32-bit Windows, but it had no DOS mode, so no luck.

Another integral tool of that config is grep. Accidentally, I found a version of grep that is shipped with Turbo C++, but in the end I did not bother and just used the vimgrep command.

Vim in DOS

Choosing a Programming Language

I had an editor, but only some batch files to edit, so I needed a programming language. The first language I learned was Turbo Pascal, and I wanted to try Turbo C++ as well (so much Turbo). I managed to get both working, but landed on QBasic 1.1. The reason is that this is the version shipped with MS-DOS 5.0, so it had the most sentimental value. For a lot of people, that was their first programming language. Now I could relive that experience. It does not have a compiler like other versions, but I’ll live.

I will return to Turbo Pascal, because I want to rebuild my first-ever program, but that is a story for another time.

All these languages come with their own IDE. They are really easy to use, with great built-in features like automatic formatting and step debugging.

QBasic IDE

I checked out DJGPP as well, which is a port of GCC to DOS and would be a great fit for Vim. I did not manage to get that working, but I may return to it as well.

Workflow with Vim and QBasic

The text editing experience is still the best in Vim, so I wanted to write the code in it. The only thing I did was create keymaps in _VIMRC to run certain commands, with certain filetypes.

autocmd FileType basic nnoremap <buffer> <leader>r :!qb /run %<CR>
autocmd FileType vim nnoremap <buffer> <leader>r :source %<CR>

This means basic files can be run with <leader>r, and Vim scripts can be sourced with the same keymap. The command qb /run % immediately runs the current file in QBasic.

This is an implementation of the great edit-compile-run cycle (without compilation, really), the only workflow you’ll need after the apocalypse.

QBasic FizzBuzz in Vim

Writing FizzBuzz in QBasic

At this point, I realized I knew basically nothing about Basic (pun intended), so let’s write FizzBuzz, the most popular programming exercise of all time, which can be done by anyone’s grandmother.

I’ll show you a method and try to collect the most amazing details:

FUNCTION FizzBuzz$ (Number)
    IF Number MOD 15 = 0 THEN
        FizzBuzz$ = "FizzBuzz"
        EXIT FUNCTION
    END IF

    IF Number MOD 5 = 0 THEN
        FizzBuzz$ = "Buzz"
        EXIT FUNCTION
    END IF

    IF Number MOD 3 = 0 THEN
        FizzBuzz$ = "Fizz"
        EXIT FUNCTION
    END IF

    FizzBuzz$ = STR$(Number)
END FUNCTION

Lot of uppercase goodness
Single equals sign for comparison
Function and variable names can end with $ to indicate they are strings
Returning a value is done by assigning to the function name
EXIT FUNCTION is used to return early
STR$ is used to convert a number to a string because there is no implicit conversion

All very logical, I like it.

The most problematic part of this solution is that with most input, most of the conditions will run, but they need to be evaluated anyway…

Then we need to loop through the numbers and print the result, so the main program is:

CLS

FOR i = 1 TO 100
Result$ = FizzBuzz$(i)
PRINT Result$
NEXT i

END

Thank you for following yet another adventurous tale. I hope you enjoyed it as much as I did. Prepare DOSBox, QBasic, and Vim, and join your next interview with confidence.

Farewell