The FileSystemObject is used in ASP to read and write text to and from a file. This powerful object can also move, delete and create new folders, and so must be used with an strong eye on the possible security implications.
Uses for the FileSystemObject include simple storage of information without a database, as well as the generation of user-created pages on a website - in other words, it's not only for files that end in .txt. It can however only write text, not binary, so you can't use it for manipulating images.
The most basic operation - writing a simple text file to the server can be done using the following code: