函数名: ecvt 
 功  能: 把一个浮点数转换为字符串 
 用  法: #include <stdlib.h> 
         char ecvt(double value, int ndigit, int *decpt, int *sign); 
 程序例: 
#include <stdlib.h> 
 #include <stdio.h> 
 #include <conio.h> 
int main(void) 
 { 
    char *string; 
    double value; 
    int dec, sign; 
    int ndig = 10; 
   clrscr(); 
    value = 9.876; 
    string = ecvt(value, ndig, &dec, &sign); 
    printf("string = %s      dec = %d \ 
    sign = %d\n", string, dec, sign); 
   value = -123.45; 
    ndig= 15; 
    string = ecvt(value,ndig,&dec,&sign); 
    printf("string = %s dec = %d sign = %d\n", 
    string, dec, sign); 
   
   value = 0.6789e5; /* scientific 
    notation */ 
    ndig = 5; 
    string = ecvt(value,ndig,&dec,&sign); 
    printf("string = %s           dec = %d\ 
    sign = %d\n", string, dec, sign); 
   return 0; 
 }