When reading or writing a disk file, are the functions described in this chapter really unbuffered? Explain.

All disk I/O goes through the kernel's block buffers (also called the kernel's buffer cache). The exception to this is I/O on a raw disk device, which we aren't considering. Chapter 3 of Bach [1986] describes the operation of this buffer cache. Since the data that we read or write is buffered by the kernel, the term unbuffered I/O refers to the lack of automatic buffering in the user process with these two functions. Each read or write invokes a single system call