Language in C 面试题与答案

Question: How do I use function ecvt( ) in a program?

Answer: The function ecvt( ) converts a floating-point value to a null terminated string. This function takes four arguments, such as, the value to be converted to string, the number of digits to be converted to string, and two integer pointers. The two-integer pointer stores the position of the decimal point (relative to the string) and the sign of the number, respectively. If the value in a variable, used to store sign is 0, then the number is positive and, if it is non-zero, then the number is negative. The function returns a pointer to the string containing digits. Following program demonstrates the use of this function.

#include <stdlib.h>
main( )
{
char *str ;
double val ;
int dec, sign ;
int ndig = 4 ;

val = 22 ;
str = ecvt ( val, ndig, &dec, &sign ) ;
printf ( "string = %s dec = %d sign = %dn", str, dec, sign ) ;

val = -345.67 ;
ndig = 8 ;
str = ecvt ( val, ndig, &dec, &sign ) ;
printf ( "string = %s dec = %d sign = %dn", str, dec, sign ) ;

// number with a scientific notation
val = 3.546712e5 ;
ndig = 5 ;
str = ecvt ( val, ndig, &dec, &sign ) ;
printf ( "string = %s dec = %d sign = %dn", str, dec, sign ) ;
}

The output of this program would be

string = 2200 dec = 2 sign = 0
string = 34567000 dec = 3 sign = 1
string = 35467 dec = 6 sign = 0