While we usually take associative array/dictionary/hash data structure as granted in modern programming languages, there is no such thing builtin in a good old C. It might be tempting to use SQLite or even Berkeley DB to fullfil that urge in many project, but the extra dependency handling is a PITA.Plus, there are many tasks that do not require ACID neither persistent storage.Even a red-black tree could be an overkill sometimes. Then, there is a bitwise trie.