struct status {
short code; /* status code */
short len; /* actual number of bytes transferred */
short lchnum; /* logical channel number */
char lchdir; /* sub-channel:recv,xmit,both */
};
/* possible values for code */
#define ST_OK 0 /* successful return */
#define ST_IARGS 1 /* illegal arguments */
#define ST_HARD 2 /* hardware failure */
#define ST_PREV 3 /* previous request already queued */
#define ST_NOPREV 4 /* no request currently queued */