Also a video controller . Not scanning frequently enough causes flicker. IBM PC uses a character-mapped display for the console. The device drivers for the terminal interface are referred to collectively as the terminal driver . The terminal driver provides a user interface through which users interact with processes accessing the terminal device.
Processes interact with the driver through the process interface .
They do not manipulate the devices directly. The lower-half interacts with the device registers and handles interrupt. The upper-half and lower half synchronize through a shared data structure. Generic picture for serial line. The two buffers are needed so that the interface between processes and the device can be asynchronous.