Programming in Practice

Im a freshman in college right now, learning C in Computer Science.

What I was mostly wondering was, how does programming work in practice? How much do you really need to know by the time you graduate from college (I plan on getting my MS, btw), and what should I spend my time learning now in my spare time outside of class?

>>1
Writing code outside of class helps a lot, but be sure to pay close attention in upper-level CS classes.  From my experience, everything I learned from my CS curriculum was only a strict subset of the knowledge I needed on the job.  Looking back, I wish I would have gotten around to taking courses in real-time systems, fault-tolerant systems, and the graduate-level courses in computer architecture and operating systems.

There are plenty of real-world applications that are so demanding that they need to be built from the hardware level upward and require custom-tailored system software.  Keep in mind that there is high performance software (and hardware) running car engines, networking and communications equipment, audio/video equipment, avionics, military weapons systems, and so forth.