#include <stdio.h>
 
int main( void )
{
    float d_n = 123.45;
    char s_cp[13] = { '\0' };
    char s_cnp[4] = { '\0' };
 
    /*
     * with sprintf you need to make sure there's enough space
     * declared in the array   
     */    
    sprintf( s_cp, "%.2f", d_n ); 
    printf( "%s\n", s_cp );
 
    /*
     * snprinft allows to control how much is read into array.
     * it might have portable issues if you are not using C99
     */
    snprintf( s_cnp, sizeof s_cnp - 1 , "%f", d_n );
    printf( "%s\n", s_cnp );
 
    getchar();
    return 0;    
}
 
/* output :
 * 123.45 
 * 123
 */