how fastread function is faster than scanf function?

please tell me that how fastread function performs faster than scanf here is the code for fastread

inline void fastread(int*a)


{

   register char c=0;

   while (c<33)

    c=getchar();

   *a =0;

   while(c>33)

   {

       *a = *a*10+c-'0';
       c=getchar();
   }

}