/* This program can find square root of any number that >=0
   and will stop when you enter a value that < 0 */
/* This version is trying to show you that we can write our
   function/procedure to solve the problem,
   though the mysqrt() is actually calling the system standard function.
   We will rewrite the mysqrt() in next version.
 *****************************/
void hello(void);    /*и穦ノ⊿把计ㄧ计hello() */
double mysqrt(double);   /*穦ノmysqrt()ㄧ计,把计琌double计 */
#include <math.h>  /* sqrt()琌math.hず */
int main()         /* 祘Α秨﹍舘 */
{
    float x;
  hello();         /* give the user some message */
  printf("X=? ");
  scanf("%f", &x);
  while(x >=0 ) {
    printf(" SQRT(%f)=%7.3f\n", x, mysqrt(x) );
    printf("X=? "); scanf("%f", &x);
  } /* while */
  return 0;
} /**************祘Αゎ***********/
void hello()
{
    printf("This program will ask you to input a value, say X.");
    printf("Then it will find the square root of X.");
    printf("The above process will continue ...");
    printf("Negative value will cease the program.");
} /* hello() */
double mysqrt(double y)
{
      double myans;
    myans = -1.0; 
    if(y < 0)  printf(" can not process negative number");
    else myans = sqrt(y);
    return myans;
} /*mysqrt*/