I am just curious to know what data structures and languages does MYSQL exactly use as back end language? and what does the file format .MYD , .MYI and .frm stand for and how does MYSQL use them?
MySQL can be compiled in C/C++ and you can download the source code to do so.
At this link, Under the Select Platform ComboBox, Select
For example, the user table for the mysql grants is amde up of three files