The word is "unless". Be careful with words like "lest" if you don't fully understand the meaning (it is not synonymous with "unless"). But no, trust me there

The word is "unless". Be careful with words like "lest" if you don't fully understand the meaning (it is not synonymous with "unless"). But no, trust me there are C programmers who use malloc and friends without knowing about the heap and stack. For those programmers it's just how you "get memory" in C. It's just part of the language for them (as opposed to part of the operating system).