bsd man page for rand

RAND(3F)																  RAND(3F)

NAME
       rand, drand, irand - return random values

SYNOPSIS
       function irand (iflag)

       function rand (iflag)

       double precision function drand (iflag)

DESCRIPTION
       The newer random(3f) should be used in new applications; rand remains for compatibilty.

       These  functions  use  rand(3C)	to generate sequences of random numbers.  If iflag is '1', the generator is restarted and the first random
       value is returned.  If iflag is otherwise non-zero, it is used as a new seed for the random number generator,  and  the	first  new  random
       value is returned.

       Irand returns positive integers in the range 0 through 2147483647.  Rand and drand return values in the range 0. through 1.0 .

FILES
       /usr/lib/libF77.a

SEE ALSO
       random(3F), rand(3C)

BUGS
       The  algorithm  returns a 15 bit quantity on the PDP11; a 31 bit quantity on the VAX.  Irand on the PDP11 calls rand(3C) twice to form a 31
       bit quantity, but bit 15 will always be 0.

4.2 Berkeley Distribution					   May 15, 1985 							  RAND(3F)