rand, srand - random number generator.


     #include <stdlib.h>

     int rand(void);

     void srand(unsigned int seed));


     The rand() function returns a pseudo-random integer  between
     0 and RAND_MAX.

     The srand() function sets its argument as the seed for a new
     sequence of pseudo-random integers to be returned by rand().
     These sequences are repeatable by calling srand()  with  the
     same seed value.

     If no  seed  value  is  provided,  the  rand()  function  is
     automatically seeded with a value of 1.


     The rand() function returns a value between 0 and  RAND_MAX.
     The srand() returns no value.


     The versions of rand() and srand() in the  Linux  C  Library
     use  the  same random number generator as random() and sran-
     dom(), so the lower-order bits should be as  random  as  the
     higher-order  bits.   However,  on  older rand() implementa-
     tions, the lower-order bits are much less  random  than  the
     higher-order bits.

     In Numerical Recipes in C: The Art (William H. Press,  Brian
     P.  Flannery,  Saul A. Teukolsky, William T. Vetterling; New
     York: Cambridge University Press, 1990 (1st  ed,  p.  207)),
     the following comments are made:
          "If you want to generate a random integer between 1 and
          10, you should always do it by

               j=1+(int) (10.0*rand()/(RAND_MAX+1.0));

          and never by anything resembling

               j=1+((int) (1000000.0*rand()) % 10);

          (which uses lower-order bits)."

     Random-number generation is a complex topic.  The  Numerical
     Recipes  in  C book (see reference above) provides an excel-
     lent discussion of practical random-number generation issues
     in Chapter 7 (Random Numbers).

     For a more theoretical discussion  which  also  covers  many
     practical  issues  in  depth,  please  see Chapter 3 (Random
     Numbers) in Donald E. Knuth's The Art of  Computer  Program-
     ming, volume 2 (Seminumerical Algorithms), 2nd ed.; Reading,
     Massachusetts:  Addison-Wesley Publishing Company, 1981.


     SVID 3, BSD 4.3, ISO 9899


     random(3), srandom(3), initstate(3),