sources

picture: 

 

https://de.wikipedia.org/wiki/C_(Programmiersprache)#/media/Datei:The_C_Programming_Language.png 

C history and basics: 

https://www.bell-labs.com/usr/dmr/www/chist.html 

https://www.geeksforgeeks.org/what-is-imperative-programming/ 

https://w3schools.tech/de/tutorial/cprogramming/c_overview 

https://www.geeksforgeeks.org/c-hello-world-program/ 

https://open-std.org/jtc1/sc22/wg14/

https://cplusplus.com/

freeCodeCamp.org

https://www.tutorialspoint.com/cprogramming/index.htm

book: Grundkurs C by Jürgen Wolf, Rene Krooß ISBN: 978-3-83627689-4

Community and publicity: 

https://stackoverflow.com/questions/tagged/c 

https://www.reddit.com/r/C_Programming/ 

https://www.geeksforgeeks.org/high-performance-computing/ 

Statistic about C, Statista: https://de.statista.com/statistik/daten/studie/678732/umfrage/beliebteste-programmiersprachen-weltweit-laut-pypl-index/ 

C23-standard: 

https://simplifycpp.org/?id=a0583