TITLE: What is the difference between language of empty string and empty set language?
QUESTION [10 upvotes]: I am reading Introduction to Automata theory by Ullman. It says the empty set and set containing empty string is different. I am unable to understand the difference between them as the empty string doesn't have any character.
Forgive me if this is dumb but I can't seem to understand it

REPLY [6 votes]: Here is a program that accepts the language that contains only the empty string:
    s = get_input();
    if (s == "") then ACCEPT;
    else REJECT;

Here is a program that accepts the empty language:
    s = get_input();
    REJECT;

They are not the same program! The first one accepts the empty string; the  second does not.