*
*## DESCRIPTION

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.

## RETURN VALUE

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

## NOTES

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.

## CONFORMING TO

SVID 3, BSD 4.3, ISO 9899

## SEE ALSO

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