Exercise solutions.
This book is amazing. Starting with some simple mathematical equations, this book teaches programmers how to structure and manage a large code base. Another side effect after reading this book is that I know how to code Scheme and found out Lisp is a beautiful and elegant language.
There are many versions of the book available online. Here is a good one https://sarabander.github.io/sicp/
If you like SICP as I do, I suggest you to buy the book to support the authors. I love to read theories and ideas on my hard-copy but while doing exercise, it is more convenient to use the soft-copy of the book.