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What is the clear program?

Typing clear at the terminal clears your screen. How does this program work? The implementation is tiny:

#include <stdio.h>
int main() {
  printf("\033c");
  return 0;
}

This magic string is composed of two bytes: 27, then 'c'. Byte 27 is ESC in the ACSII table, and it’s understood by the terminal as an escape sequence. It then expects further characters to specify the command; we give it 'c' which clears the screen.

What can computers do? What are the limits of mathematics? And just how busy can a busy beaver be? This year, I’m writing Busy Beavers, a unique interactive book on computability theory. You and I will take a practical and modern approach to answering these questions — or at least learning why some questions are unanswerable!

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After months of secret toil, I and Andrew Carr released Everyday Data Science, a unique interactive online course! You’ll make the perfect glass of lemonade using Thompson sampling. You’ll lose weight with differential equations. And you might just qualify for the Olympics with a bit of statistics!

It’s $29, but you can get 50% off if you find the discount code ... Not quite. Hackers use the console!

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