Question: what are the different classification of operating system

title: Operating system
text: The key design goal of device drivers is abstraction . Every model of hardware ( even within the same class of device ) is different . Newer models also are released by manufacturers that provide more reliable or better performance and these newer models are often controlled differently . Computers and their operating systems can not be expected to know how to control every device , both now and in the future . To solve this problem , operating systems essentially dictate how every type of device should be controlled . The function of the device driver is then to translate these operating system mandated function calls into device specific calls . In theory a new device , which is controlled in a new manner , should function correctly if a suitable driver is available . This new driver ensures that the device appears to operate as usual from the operating system 's point of view .