The lack of abstraction is what makes C faster. If you write an output statement you know exactly what is happening. If you write an output statement in java it is getting compiled to a class file which then gets run on a virtual machine introducing a layor of abstraction. The lack of object oriented features as a part of the language also increases it's speed do to less code being generated. If you use C as an object oriented language then you are doing all the coding for things such as classes, inharitence, etc. This means rather then make something generalized enough for everyone with the amount of code and the performance penelty that requires you only write what you need to get the job done.
