Freeshooter92 said
Exactly. Though it isn't impossible since maybe the information exist in a ruin somewhere, or maybe people invented a magical alternative.
Maybe the information is out there, sure, but... Keep in mind most of that stuff is digital in our world. After so much time left without maintenance and power, the generators would be useless, and the computers housing such information would be near inaccessible. And even if you did access the computers, would you know the passwords to get such classified material? Would you have the hacking expertise to get through the machine's firewalls? Would the hard drive be intact?
Maybe there is a machine in perfect state out there somewhere, but I doubt it's unprotected by firewalls and a huge password!
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Also, what Fallen said. I rather enjoy the Fantasy setting we're in now. I don't think it's necessary to add guns or any kind of advanced technology!