= seconds,  ticks,  HZ,  MS2HZ,  MS2TK,  TK2MS, TK2SEC: kernel times and time conversions     long    seconds(void)     ulong   ticks(void)        #define HZ          ...    #define MS2HZ(t)    ...    #define TK2SEC(t)   ...    #define TK2MS(t)    ...    #define MS2TK(m)    ... Seconds returns the system's idea of the current time as  thenumber of seconds since the start of the epoch (00:00:00 GMT,January 1, 1970). Ticks returns the  number  of  system-dependent  clock  tickssince system boot. The  system  clock  frequency is platform-dependent.  Severalsymbolic constants and macro functions  are  defined  by  thefile mem.h to convert between different time units: HZ     The number of clock ticks per second. MS2HZ  Milliseconds per clock tick. TK2SEC(t)       Convert t clock ticks to seconds and return the result       (truncating not rounding). TK2MS(t)       Convert t clock ticks to milliseconds and  return  the       result. MS2TK(m)       Convert  m  milliseconds to clock ticks and return the       result (truncating). The functions are often used to calculate delays  for  timingfunctions, for instance:        if(atactlrwait(dp->cp, DHmagic, 0, MS2TK(100))){               ...       }