c programming: program to convert non decimal number system to decimal

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C

void main()
{
 long n,dec,mult,r,base;
 clrscr();
 printf("\n Enter a base : ");
 scanf("%ld",&base);
 printf("\n Enter a number :");
 scanf("%ld",&n);
 dec = 0;
 mult=1;
 printf("\n Decimal equivalent of base %ld number %ld is ",base,n);
 while ( n != 0 )
 {
  r = n % 10;
  n /= 10;
  r = r * mult;
  dec = dec + r;
  mult *= base;
 } 
 printf("%ld",dec);}

this program converts the integer part of any number system of base 2, 8 &16 to decimal. please tell me wht command shld b given 2 calculate the fractional part also. i need it urgently plz help.