THAT would suck. Here's some things I've noticed at work.
They wouldn't be able to perform boolean logic:
Me: "Do you have either a service ticket OR a phone number I could get?"
Them: "No"
Me: "Could I get the phone number?"
Them: "Yes its ##########"
Me: "Lets click start AND then run"
Them: "Okay I clicked start, now what?"
They wouldn't be able to parse strings:
Me: "Could I get the serial number off the back of the unit, it will start with CN"
Them: "STR1234"
Me: "That's not the right one, it starts with CN"
Them: "I don't see anything with CN"
*this carries on for a good 5 minutes until they find it*
They wouldn't be able to do comparisons:
Me: "Are you using a USB cord or an Ethernet cord? The Etherney cord looks like an oversized phone cord."
Them: "Ethernet."
*really its USB, or the opposite may occur as well*
And this one isn't compiler related but, they would be a lot like Vista:
Me: "Click uninstall"
Them: "You want me to click uninstall"
Me: "Yes."
Them: "Okay it asks if I want to uninstall it. Do I want to uninstall it."
Me: "Yes."
Them: "Okay it asks if I should continue, should I continue?"
Me: "Yes."
I'm sure there's lots more too. It'd just be bad news.
