[1] There are many ways that could manually create a zero-byte file, for example, saving empty content in a text editor, using utilities provided by operating systems, or programming to create it.
Because writes are cached in memory and only flushed to disk at a later time (page cache), a program that does not flush its writes to disk or terminate normally may result in a zero-byte file.
Some very simple formats do not use metadata, such as ASCII text files; these may validly be zero bytes (a common convention terminates text files with a one- or two-byte newline, however).
IF Exist - Testing: Use the zero-byte (zero length) file as an "exit" ramp or for a "goto" statement within a batch-file or script.
It provides a directory listing, but requires no disk space.