The absolut hardes thing I found was when I searched for a bug in a Module written in some kind of PL/I. I tried to understand, why a special line of code does not work, using 'true' and 'false' Boolean statements... now ... my forerunner was able du redefine true and false so that true was 0 and false was -1 ... incredible!

Years ago, another developer told me about a special coding horror... he had an developer that falled in love and so he called for the next module all his variables with the name of his beloved... from Susi001 to Susixxx :) Now, try to read such a program ...