A computer scientist walks into a bar, holds up his pointer finger and says, "Two drinks, please."
The bartender’s confused, but gets the computer scientist his drinks, and carries on.
The computer scientist finishes his drinks, holds up his pointer finger again and says, "Two more drinks!"
So the bartender comes over and asks the computer scientist, "You know, you keep asking for two drinks, but you only hold up one finger. What's the deal?"
The computer scientist says, "What do you mean? I asked for two, I showed you two."
The bartender says, "No, you only showed me one. Now, show me again, how many drinks do you want?"
The computer scientist holds up his pointer finger.
The bartender pours him one drink.
As the bartender starts to walk away, the computer scientist asks, "What about my other drink?"
To which the bartender raises his middle finger.
The computer scientist then asks, "Four what?"
Source: Just wrote this joke