What does "!" mean in pseudo-code? I know "!" stands for factorial but I can't translate it

Question

What does ! mean in pseudo-code? I know ! stands for factorial but I can't translate it .

ex:

get operation

if (operation!= ’B’ OR operation != ’D’ OR operation!= ’W’) then
    print "Invalid Operation"

What does it mean?

Answer 1

!= means not equal and ! generally means not or negation.