Really? It's a bit of a nonsense that I did so long ago so it's weird to hear someone interested in it...

The script has been lost to time. I wrote it 5+ computers ago and I don't even know where input that backup...

The overall gist is that CGI Bin specification sets Environmental variables, STDIN and STDOUT to various values. A minimal pure assembly that writes <h1> Hello World </h1> over stdout is your minimalist CGI Script.

A bit of research into what those STDIN/Environmental variables is needed for more. I knew this may e 20+ years ago but have long forgotten....

With access to the various input parameters offered over CGI, you can easily access form data (buttons and whatever clicked by the user). Use some smart file writing to store sessions and off you go....

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Maybe start with a Perl CGI tutorial. Then go backwards to C, and finally raw assembly by hand