About using compact flash with mp3 files?

Thanks,

but i wanna focus on these words" Another alternative is to use the new (in 5.0) host file system. This allows you to open a file through JTAG (the file resides in your PC, but Nios opens it just as if it were there in its own private file system)."

1)How does the nios actually opens the file on the PC(i mean does [fopen] works in this case or what?)

2) Will this need an operating system or i can do without it?

Thanks,