You hard drive is a mass storage media device. It's basic purpose aside from usually being a boot device is a means of storing and retrieving large amounts of data at a high rate of speed.
The hard drive can be written to over and over again.
Over a period of time depending on the amount and type of use it's necessary to perform certain maintenance procedures on this device to keep it's performance up to adequate levels and your expectations.
Due to the size that hard drives have become today, larger mediums are required for backing up the data on these drives. Enter the DVD R/W drives.
DVD R/W Drives
DVD R/W drives are not just cd burners. They're high density cd burners. The regular cd r/w can write up to 700mb of data at various speeds on the disk. The DVD burner writes upwards of 9Gb of data on a specially formatted disk. It's looks the same as a regular disk but by far is not the same. The method of data formatting and compression is far greater than on a regular cd burner.
Due to the size of today's hard drives, dvd burners are becoming the most resourceful method for backing up the data from these high capacity drives.
I/O cards are internal devices that plug directly into slots inside the computer. This puts their signals directly on the signal bus where they compete with other devices both internal and external for processor time.
I/O cards require system resources such as irqs, addresses, sometimes a dma and drivers in order to function properly. A driver is simply a software file that tells the system the parameters and operating specs of the device that it belongs to. It's sort of like an introductory note to the teacher from a new students parents telling the teacher his name, address and what he likes, doesn't like and is allergic to.
Once the system has the info file it assigns resources to that device and then it is recognized when it requests attention from the processor.