106.产生随机数

/* 在BC31下编译 */
/* compile under Borland C++ 3.1 */
#include <stdio.h>
#include <sys\timeb.h>
#define Alpha 3.90
double initvalue();
double random(void)/*返回一个(0,1)之间的随机数*/
{
    static double f=-1.0;
    double initvlaue();
    if(f==-1.0) f=initvalue();
    else f=Alpha*f*(1.0-f);
    return f;
}
double initvalue()/*返回随机数序列初值*/
{
    double f0;
    struct timeb *pr;
    for(;;){
    ftime(pr);
    f0=pr->millitm*0.9876543*0.001;
    if(f0<0.001) continue;
    break;
    }
    return f0;
}
void main()
{
  double test;
  int i;
  clrscr();
  puts("This is a random number generator.");
  puts("\n The random number are: ");
  for ( i = 0; i < 3; i++ )
  {
    test = random();
    printf ( " >> rand%d:%f\n", i, test );
  }
  puts("\n Press any key to quit...");
  getch();
}