Most functions simply change the appropriate control parameter.
It waits on isem , reads the character at the tail of the input buffer without changing the tail pointer, and signals isem since the character was not actually consumed. A procedure ttyinit is called to do device-specific initialization of the dispatch table entry, device registers, and control block of each SLU device. For efficiency reasons, it changes the input and output code of in the dispatch table from the minor number to a pointer to the control block. Initializes control parameters. Initializes other parameters.