Practice code and exercise solutions for the book C programming by K.N. King 2nd Edition. This book is a pretty thorough introduction to C up until the 1999 standard. Many useful features were added to the language in the 2011 standard (multi-threading, anonymous unions, etc), see https://smartbear.com/blog/c11-a-new-c-standard-aiming-at-safer-programming/, which is not covered by this book.
As the problems were only used to aid learning, no effort was made to perfect code quality.