Programming

#include <stdio.h>
#include <ctype.h>

int main () {
   char coll[2];
   int col;

   do {
       printf("Enter Number: ");
       scanf("%s",coll);

       if (isdigit(coll[0]))
       {
           col=((int)coll[0])-48;
       }
       else
       {
           printf("It is not a digit : %c,%d\n",coll[0],coll[0]);
       }

   } while (( col < 4  ) || (col >9));
}