macro allows a unique device number to be generated based on its
macros can be used to obtain the original numbers from the device number
In previous implementations of
all block and character devices were uniquely identified by a pair of
major and minor numbers.
The major number referred to a certain device class (e.g. disks, TTYs)
while the minor number identified an instance within the device class.
Later versions of
automatically generate a unique device number for each character device
These numbers are not divided in device classes.
these macros are only used by utilities that need to exchange numbers
with other operating systems that may use different encodings for
.Vt dev_t ,
but also applications that present these numbers to the user in a more