Why a multi-tasking operating system?
A multi-tasking operating system can allow the application to continue immediately after it does a write, and the actual disk write can happen later. This is known as write behind. The operating system can also read several blocks from the file when the application requests just part of the first block. This is known as read ahead. When the application requests the block later on, the block will already be there and the OS can then schedule some more reads. A multitasking operating system is required because these operations can cause interrupts and processing when control has been given back to the application. Basically, operating systems such as DOS, MS-Windows, MacOS and such do not allow true preemptive multitasking and can not do the read a heads and the write behinds. For these systems, the latency of a disk drive is the most important thing. The application does not regain control until the read or write has finished. *** The controller can’t speed up the disk. Remember, the bo
