I understood studying the filesystem api files are written to a specific directory(temporary or persistent), I wonder if it is possible to write to a accessible directory thing as "c: \ files"
Short answer: No. This has been covered many times before here. I explained more fully in my reply to JS Filesystem API: accessing JS FileEntry's on local system?.
If you want a tutorial of the File System API, try Exploring the FileSystem APIs on html5rocks.com