Another pointless project - this time for MS-DOS - and how good is Claude?

I've been looking at old MS-DOS applications and started thinking about what would have been a useful application for MS-DOS, with all the knowledge we have now.

The only thing I could think of was how MS-DOS could have been made easier to select files and folders and launch applications.

I know there were plenty of GUI and TUI applications that made it easy to manipulate files, but I think it might have been nice if the MS-DOS command line had autocomplete to help you out.

Instead of having to do lots of CD and DIR and having to know a file path and name before you could run a command, imagine being able to start typing COPY and then you would be presented with the first match in the current folder and then use the arrow up and down keys to select a file or folder.

Or how about being able to launch an executable or batch file just by typing the name, or having a list of file extensions and associated applications so you could open the file in the application by typing or selecting the filename.

Maybe there was something like this for MS-DOS that I never discovered, or maybe this exists now in Windows or Linux? Let me know because I don't know.

Anyway, I thought I might mock up a simple application to do this "for fun", and I looked at what language I could do this in without too much effort. QuickBasic 4.5? Doesn't seem to support getting a list of files very well (PDS 7.1 looks to do it, though). Turbo Pascal? Seemed to do what I needed but I'd never used Pascal before and probably not the most useful skill to learn in 2025. C? I've done plenty in C# but nothing in C for a couple of decades.

While I was asking AI for advice on which programming language to use, I thought maybe I should just get AI to do the whole job. Things have changed for me in 2025 and it's hard to put a few hours work into something when you can just instruct someone (oops, something) else to do it and then tell them what they got wrong.

I gave Gemini a go and it did pretty good for a proof-of-concept, but then I got greedy and wanted more, so I switched to Claude (Sonnet 4.5) and after some detailed instructions, and then many fixes and tweaks, I got a fully-functional system that seems almost production ready.

I am once again amazed at what AI can do. I didn't have high expectations as I thought developing for MS-DOS would not be possible (having once failed when I asked for some Commodore 64 BASIC work), but Claude once again proved itself as the best programming AI (to me, at least, and I also tried ChatGPT).

Claude called the application "Enhanced Command Prompt v1.0" but named the files "CMDPLUS", so I went with all of that.

After you start the application you are greeted with some introductory text and then what looks like a normal command prompt.

You type a character and autocomplete will kick in and suggest any matching known command. You can either keep typing, press up or down to cycle through any matches, or press tab to accept the current suggestion. The enter key will also accept any current suggestion and also execute the command.

Some commands accept a file path or file name as a parameter and if you start typing after the command name you will get autocomplete for paths and file names. Commands like copy will also take a second file.

Any parameters starting with a forward slash or hyphen will be treated as such. No autocomplete is available for these, although might be a nice feature.

I wasn't sure how best to distinguish between a command and starting an executable file or batch file so I went Linux-style so if you start typing with a path character like a drive specifier, back slash or a full stop or two followed by a back slash then you will be able to select a file to execute. If the file's extension is on the list of known extensions then the corresponding application will be started with the file path/name as the parameter.

Autocomplete can be cancelled by pressing the escape key, if needed.

Like DOSKEY MS-DOS 5+, a command history is available, so you can press cursor up and down to cycle through previous commands.

I was also thinking it might be handy to know the number of files affects when pattern matching characters are used when deleting, copying, etc, so Claude added a confirmation message when you use these commands and pattern matching characters with the number of files matched.

Most options are managed in a configuration file called "CMDPLUS.CFG", although it is optional.

One feature I thought would be very useful was the ability to record past screen pages so you could use page up and down to move around the last few pages. I didn't have much luck with this but will try again in a future post.

Download CMDPLUS.ZIP, a compressed file containing C++ source, executable and sample configuration file.

Update: So it turns out back as far as the 1990s there were applications that did all this and more. There are some good examples on this page. Even Windows command prompt has a form of autocomplete that I had never known about until now.