In order to solve larger problems, we often need large programs. All of the programs we have developed here have been small—under 1,000 lines of code. A reasonable size for a medium-sized program to, say, create a simple game, perform a basic but robust utility, or keep notes might consist of anywhere between 10,000 to 100,000 lines of code. A large program would manage a company's inventory, track sales orders and bills of materials, provide word processing or spreadsheet capabilities, or manage the resources of the computer itself—an operating system. Such programs would consist of anywhere from 100,000 lines of code to a million or more lines of code. Such programs would have teams of programmers and require hundreds of man-years of effort to create and maintain them.

As you gain experience in programming, you may find that the kinds of problems you work to solve become...