A computer system uses simplified device drivers for operating hardware devices.
A simplified device driver for a hardware device of a given device type, such as
a flatbed scanner, works with a system-supplied common driver for that given device
type. The common driver and the simplified driver together function like a regular
device driver. The simplified device driver implements a small number of entry
point functions corresponding to a pre-selected set of operation commands "generic"
to hardware devices of that given device type. When an application makes a request
for an operation by the device, the request is passed through a device driver interface
(DDI) to the common driver. The common driver then calls the entry point functions
in the simplified device driver to carry out the requested operation.