Using a few handy open source libraries, you can make your applications able to natively read DXF and DWG files on any operating system at no cost.

借助几个便捷的开源库，您的应用程序就可以读取任何操作系统上的DXF和DWG文件，并且不产生任何成本。

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Where there is no public power grid, the PV systems currently operate cost-effectively, due to their low operating costs.

在没有公用电网的情况下，由于系统的低运营成本，就它们当前的表现来看这一系统的成本是可以接受的。

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To set up a serial console under Windows XP or Vista operating system, I recommend downloading PuTTY, a terminal emulation program for Windows available at no cost (see Resources).

对于在Windows XP或Vista操作系统上设置串行控制台，我建议下载PuTTY，这是一个用于Windows操作系统的免费终端模拟程序(见参考资料)。

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Although Air Force One's operating costs per person far exceed the cost of even a first-class commercial ticket, the logic is that it's unfair to charge the president's campaign for the full cost of operating Air Force One because he has no choice but to fly on the presidential plane for security reasons.

CNN: The perks of presidential travel

In 2008, Google launched the open-source Android operating system, licensing mobile software to any and all device makers (at no cost), allowing others to tweak their code and innovate without permission.

WSJ: Thomas Hazlett: The iPhone Turns Five