Why on Earth are you learning/using C? There is so much emphasis on OOP these days that you're essentially confining yourself to a very small, specialized area.
Personally, maybe 5,000 lines. I cannot remember. It utilized an OpenGL library for Java. Anything graphic intensive will require far more lines of code.
As others have stated, it is quite common to have to modify/enhance/fix systems with millions of lines of code in the industry.







