what is r+ in FILE structure in C?

Question

I am reading some C text at the address: https://cs.senecac.on.ca/~btp100/pages/content/files.html

in the section \"OPENING A FILE\", the author wrote:

Answer 1

Of course, there are some writing into a file which can fail (think of a "disk is full" situation).

The "possible writing" phrase means just that a FILE* handle fopen-ed with "r+" might be used without any write operations. For instance, if your application want to overwrite some part of the file only under some circumstances, it can avoid the writing.