Computer Science Students

A question is asked to CS department students. The question is: What is
the value of `2*2′?

(1st year student): says `4′, without any thinking.

(2nd year student): says `4, exactly’, after a moment of thinking.

(3rd year student): takes a pocket calculator, presses some buttons and
says `4′.

(4th year student): writes a program of about 100 lines, debugs it, runs
it and says: `4.0e+00′.

(5th year student): designs a new programming language that perfectly
fits for solving such problems, implemets it, writes a program, and
answers: `It says “4″, but I doubt if I really fixed that ugly bug last
night…’

(student just before the final graduation exams): cries in desperation:
`Why, why do you think I must know all that bloody constants by heart?!’