Does anyone know of a good random number generator in C?  I know of the
random generators in Numerical Recipes.  Are there other good sources?
Thank you in advance.

    There are plenty of other generators that can be
implemented in C -- or in C++, or Pascal, or Ada, or
Fortran, or Lisp, or perl, or what-have-you.  All of
which means that your question isn't "a C question"
and really doesn't belong here.

<off-topic>
        http://random.mat.sbg.ac.at/news/
</off-topic>

Probably the most common type has k=1, and needs a single seed,
with each new integer a function of the previous one.
An example is this congruential RNG, a form of which was the
system RNG in VAXs for many years:

   static unsigned long x=123456789; /* a random initial x to be
*/
                                                        /* assigned by the
calling program */
   unsigned long cong(void )
   { return (x=69069*x+362437);}

Simple, k=1, RNGs can perform fairly well in tests of randomness such as
those in the new version of Diehard,
           csis.hku.hk/~diehard
but experience has shown that better performances come
from RNGs with k's ranging from 4 or 5 to as much as 4097.

Here is an example with k=5, period about 2^160,
one of the fastest long period RNGs, returns more than
120 million random 32-bit integers/second (1.8MHz CPU),
seems to pass all tests:

static unsigned long
x=123456789,y=362436069,z=521288629,w=88675123,v=886756453;
      /* replace defaults with five random seed values in calling program */
unsigned long xorshift(void)
{unsigned long t;
 t=(x^(x>>7)); x=y; y=z; z=w; w=v;
 v=(v^(v<<6))^(t^(t<<13)); return (y+y+1)*v;}

Another example has k=257,  period about 2^8222.
Uses a static array Q[256]  and an initial carry 'c',
the Q array filled with 256 random  32-bit integers
 in the calling program and an initial carry c<809430660
for the multiply-with-carry operation.
It is very fast and seems to pass all tests.

static unsigned long Q[256],c=362436;  /* choose random initial c<809430660
and */
                                       /* 256 random 32-bit integers for Q[]
*/

unsigned long MWC256(void){
  unsigned long long t,a=809430660LL;
  static unsigned char i=255;
     t=a*Q[++i]+c; c=(t>>32);
     return(Q[i]=t);      }

The Mersenne Twister (check Google) is an excellent RNG,
with k=624. But it requires an elaborate C program and is
slower than many RNGs  that do as well in tests,
have comparable or longer periods and require
only a few lines of code.

Here is a complimentary-multiply-with-carry RNG
with k=4097 and a near-record period, more than
10^33000 times as long as that of the Twister.
(2^131104 vs. 2^19937)

  static unsigned long Q[4096],c=362436; /* choose random initial
c<809430660 and */
                                                                /* 4096
random 32-bit integers for Q[]       */
  unsigned long CMWC4096(void){
  unsigned long long t, a=18782LL;
  static unsigned long i=4095;
  unsigned long x,r=0xfffffffe;
     i=(i+1)&4095;
     t=a*Q[i]+c;
     c=(t>>32); x=t+c; if(x<c){x++;c++;}
     return(Q[i]=r-x);    }

You will find several more CMWC RNGs and comments on
choice of seeds in the May 2003 Communications of the ACM.

Thanks for telling me so many good random number generators.
However, may I know where I can find the routines you are referring to?  
For example, cong(void), MWC256(void) and CMWC4096(void).  Thank you in
advance.

David

David

  If you are using Linux, you can read from /dev/random or,
/dev/urandom ( They generate random numbers based on the input of
hardware devicesm, such as mouse, or keyboard.

  Siddharth.