A 20-year-old junior at Georgia Southern University told BuzzFeed News that she normally spends $500-600 on access codes for class.

As universities go digital, students are complaining of a new hit to their finances that's replacing—and sometimes joining—expensive textbooks: pricey online access codes that are required to complete coursework and submit assignments.

But critics say the digital access codes represent the same profit-seeking ethos (觀念) of the textbook business, and are even harder for students to opt out of.

Changing building codes, evolving tastes, and the high cost of maintaining those wonderful old signs have businesses embracing LEDs, which are energy efficient, but still carry great cost.

David Hunt, an associate professor in sociology at Augusta University, which has rolled out digital textbooks across its math and psychology departments, told BuzzFeed News that he understands the utility of using systems that require access codes.

Digital learning systems now charge students for access codes needed to complete coursework, take quizzes, and turn in homework.

Many of the access codes he's purchased have been required simply to complete homework or quizzes.

Some colleges have what they call an "honor code", though if you are smart enough to get into these schools, you are either smart enough to get around any codes or hopefully, too ethical to consider doing so.

If, for example, building codes included green construction guidelines, most developers would be too lazy to challenge them.

In war time, codes are especially important.

As long as there have been codes, people have tried to break them.

People have used secret codes for thousands of years.

Secret codes keep messages private。banks, companies, and government agencies use secret codes in doing business, especially when information is sent by computer.

So codes must be changed frequently.