The C programming language
Sergey Abbakumov
https://www.amazon.com/Programming-Language-2nd-Brian-Kernighan/dp/0131103628. This is a truly legendary book on programming. Just imagine: 34 editions! Many people can say: "Why do I need this outdated language?" In fact, I agree with Bobuk (@bobuk). Every self-respecting programmer must understand well what is happening "under the hood". It is desirable to know how the modern processor, memory and cache work. The C language is a portable macro-assembler that allows you to play around with the computer and squeeze out the maximum performance from it.
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