004 lecture-in-text-format
https://ckmobile.medium.com/node-js-modules-21f699a75aba

005 article-version
https://ckmobile.medium.com/how-to-work-with-files-and-directories-using-the-fs-module-in-node-js-a16c9308aea8

006 article-version
https://ckmobile.medium.com/buffers-and-streams-in-node-js-d71511291cde