In one case, the professor didn't require students to buy a textbook, just an access code to turn in homework.

有一次，教授并没有要求学生购买教科书，只是需要作业提交的访问码。

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Because it's all digital, it eliminates the used book market and eliminates any sharing, and because homework and tests are through an access code, it eliminates any ability to opt out.

因为它全是数字化的，它淘汰了二手书市场，也杜绝了任何共享，而且因为作业和考试都是通过准入码进行的，它让人们失去了选择退出的任何能力。

youdao

But because it's all digital, it eliminates the used book market and eliminates any sharing, and because homework and tests are through an access code, it eliminates any ability to opt out.

但因为它全是数字化的，它消除了二手书市场，也消除了任何共享，而且因为作业和考试都是通过准入码进行的，它消除了任何选择退出的能力。

youdao

Sign up for an access code at the source to give it a try for yourself, or take a stalker-esque trip down an Engadget editor's social network tracks at the second link below.

ENGADGET: Vizify offers free infographics all about you, makes you feel like a big shot

It's very easy to set an AirPlay access code onto an Apple TV.

ENGADGET: Ask Engadget: what's the best way to arrange a protected AirPlay setup?

Mr. Bush: You should be able to instruct all of the doctors that you see to make your records available through a portal, and if you get stuck in an emergency room somewhere, there ought to be an emergency access code, that any doctor in the country can look up your chart.

WSJ: Boss Talk: Updating Doctors' Offices With the Help of Cloud Services