well i first saw this line orf code on a friends nick name on msn
it means keep thinking till the end in a C++ syntax
while "means as long as this is the only clear thing here i guess"
while takes a condition which returns either true or false the condtion is END which will weirdly mean as long as it's the end think whihc is weird plz note the " ! " sign it means NOT
so it becomes as long as it's not the end the Braces "()" indicate a contaiiner of the condition
then a curly pair of brackets indicates the actions when the result of what's between the braces 
so think is a method that needs not more clarification so it has a pair of braces a simicolon inidcates " that's it "
