输入一个整数范围（a到b）。把这个范围内的数都用素数相乘的表示方法打印出来。。。用C语言写！！！！

#include "stdio.h"

int main (void)
{
int a, b, i;
int factor_of ( int a );

printf ("请输入一个整数范围: ");
scanf ("%i%i", &a, &b);
printf ("结果是:\n\n");

for ( i = a; i <= b; ++i ) {
if ( i < 0 ) {
printf ("%i = -", i);
a = -i;
}
else {
printf ("%i = ",i);
a = i;
}

if ( factor_of( a ) == 0 )
if ( a == 1 )
printf ("无素因数，但不是素数\n");
else
printf ("素数\n");
}

}

int factor_of ( int a )
{
int i;

for ( i = 2; i <= a/i; ++i )
if ( a % i == 0 ) {
printf ("%i * ", i);

if ( factor_of ( a/i ) == 0 )
printf ("%i\n", a / i);

break;
}

if ( i > a/i )
return 0;
}