#include <math.h> 
                                                                                                                             
   #define D 2147483647.0
   #define pi 3.1415926
                                                                                                                             
   {
      long int r1,r2;
      int seed;
      double sd,rf1,rf2,norm;
                                                                                                                             
      cout << "Enter a seed" << endl;   // each time program is run new random numbers
      cin >> seed;                      // are generated.
      srandom(seed);
                                                                                                                             
      cout << "Enter standard deviation" << endl;
      cin >> sd;
                                                                                                                             
                                                                                                                             
      for (i=0;i < n ;i++)       // generate a bunch of random numbers
       {
          r1 = random(); r2 = random();
          rf1 = r1/D; rf2 = r2/D;   // convert to random float in (0,1)
          norm = sd*sqrt(-2.0*log(rf1))*cos(2*pi*rf2);
                                                                                                                             
            ......
                                                                                                                             
                                                                                                                             
       }
     ........
   }