It would be helpful to note that some of the variables used in the first two function examples are defined further down the page. I was trying to understand how

It would be helpful to note that some of the variables used in the first two function examples are defined further down the page. I was trying to understand how his first loop in add_to_free_list worked and couldn't figure out how because *freep was never declared anywhere and that was his list of free blocks. Took me a page of scribbling pointer diagrams and 5 minutes to figure out that it was declared and set further down the page as a global.