Manual memory management, mostly. Also, since C is a simpler language, its building blocks map more closely with what actually happens on hardware level (or the

Manual memory management, mostly. Also, since C is a simpler language, its building blocks map more closely with what actually happens on hardware level (or they used to... back in the 1970's). Then, there's the fact that you do not have direct access to native OS primitives from Java (i.e. system call vs stdlib function), but it has to do more with the run-time environment than the language itself.