How to Run the Khan Academy Off‑Line

With a basic knowledge of HTML, you can tailor this complex app to your needs

4 min read
Illustration: Jesse Lefkowitz
Illustration: Jesse Lefkowitz

When a friend recently asked for volunteers to help tutor inmates at a local prison, I asked, “Why not use the Khan Academy?”

This website contains a wealth of video tutorials that span a wide range of topics and complexity, ideal for inmates seeking high school equivalency diplomas. The math offerings are probably the most complete—ranging in difficulty from basic addition to linear algebra and calculus—but the site has lessons in astronomy, art history, economics, chemistry, biology, physics, and more.

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From WinZips to Cat GIFs, Jacob Ziv’s Algorithms Have Powered Decades of Compression

The lossless-compression pioneer received the 2021 IEEE Medal of Honor

11 min read
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Photo: Rami Shlush
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Lossless data compression seems a bit like a magic trick. Its cousin, lossy compression, is easier to comprehend. Lossy algorithms are used to get music into the popular MP3 format and turn a digital image into a standard JPEG file. They do this by selectively removing bits, taking what scientists know about the way we see and hear to determine which bits we'd least miss. But no one can make the case that the resulting file is a perfect replica of the original.

Not so with lossless data compression. Bits do disappear, making the data file dramatically smaller and thus easier to store and transmit. The important difference is that the bits reappear on command. It's as if the bits are rabbits in a magician's act, disappearing and then reappearing from inside a hat at the wave of a wand.

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