Random without parameters
Simple: random() isn't an Arduino function - it's a standard C function.


  Function random()
  
  long random(void)
  
  The random() function computes a sequence of pseudo-random integers in the range of 0 to RANDOM_MAX (as defined by the header file &lt;stdlib.h&gt;).
  
  The srandom() function sets its argument seed as the seed for a new sequence of pseudo-random numbers to be returned by rand(). These sequences are repeatable by calling srandom() with the same seed value.
  
  If no seed value is provided, the functions are automatically seeded with a value of 1.
  
  -- AVR LIBC Manual Page