Are the file formats such as hd0,fd,rts and vfat predefined in UNIX?

Answer: Unix supports all types of file systems from any hardware or device. Does it mean that Unix has all file formats predefined in it somewhere in libraries?

You are not asking the right question. File systems are different from file formats. So, lets do some digging.

1.
Let us consider a 2GB hard disk. This hard disk can be used in a Unix machine or a Windows machine. The only support needed in the operating system to use this hard disk is the hard disk device driver.

2.
Once the operating system recognizes this disk (through the device driver), how does the operating system use this disk?? I.e. how does the operating system store and retrieve information from this disk?? How does it know where to store and where to retrieve data from, etc

3.
To manage disk space, we need a software abstraction called File System software. We can use it without a file system also, but that is beyond the scope of this discussion. We need File System software to manage the use of the disk space, support creation/deletion of files, etc.

4.
Each operating system has code already inbuilt into the operating system to support a few file systems. For example, Linux supports ect3, Reiser FS, etc. Each file system has pros and cons and is used for different purposes. So, when we say Linux has support for multiple file systems, you can understand what it means.

5.
File formats are different from File systems. Each file in a file system can be of different file formats. For example, on Unix, we have the ELF file format for executables, on Windows/Dos, we have the .exe file format, etc. This is a special type of file that has some pre-defined organization. This predefined organization has its own uses. You can read about the file formats and their need/uses on the web.

6.
Lets come to your question. You mention hd0, rts, fd, vfat as file formats. I am not aware of file formats like that. vFat is a Linux file system that can read Windows FAT file system disk. hd0 is hard disk zero. Dunno what is rts and fd. With the above explanation, I am hoping you can dig for more information on your own.

Hope this helps.

Post of sk_seeker:
Point 4: "For example, Linux supports ext3,..." [ typo error only, required to point as person with the question seems quite a novice].

As its been pointed, that you are not asking the right question simply shows that you are confused about these tech stuff... Being a big topic, references can be given to read on them more in depth.

But for short, file formats are different from hd0, fd, rts, and vfat.
file formats is method of organizing a file with specific meanings attached.
hd0, fd is could be hda, hda1, ... and fd could be floppy device.

For any functionality to work, the functionality must be first built into the system or predefined as you call it. Similar to have the ability to read something written in english simply means you must first have knowledge of the english language.

You should read Unix Programming by M. Bach