Long-held, incorrect programming assumptions
I am doing some research into common errors and poor assumptions made by junior (and perhaps senior) software engineers.
What was your longest-held assumption that was eventually corrected?
For example, I misunderstood that the size of an integer is not a standard and instead depends on the language and target. A bit embarrassing to state, but there it is.
Be frank; what firm belief did you have, and roughly how long did you maintain the assumption? It can be about an algorithm, a language, a programming concept, testing, or anything else about programming, programming languages, or computer science.
Answer
For a long time I assumed that everyone else had this super-mastery of all programming concepts (design patterns, the latest new language, computational complexity, lambda expressions, you name it).
Reading blogs, Stack Overflow and programming books always seemed to make me feel that I was behind the curve on the things that all programmers must just know intuitively.
I've realized over time that I'm effectively comparing my knowledge to the collective knowledge of many people, not a single individual and that is a pretty high bar for anyone. Most programmers in the real world have a cache of knowledge that is required to do their jobs and have more than a few areas that they are either weak or completely ignorant of.