r = readln1(fdin1,buf1,1024);
  s = readln1(fdin2,buf2,1024);
...
while(r>0 && s>0 && flag == 0)
   {
      int i,n;

      if(r<s) n=r;
      else n=s;

      for(i=0; i<n; i++)
      {
         if(buf1[i] != buf2[i])
         {
            char sChar[10];
            int sizeChar = intToString(sChar,i+1);

            char sLine[10];
            int sizeLine = intToString(sLine,nLine);

            write(1,argv[1],strlen(argv[1]));
            write(1," ",1);
            write(1,argv[2],strlen(argv[2]));
            write(1,": char ",7);
            write(1,sChar,sizeChar);
            write(1,", line ",7);
            write(1,sLine,sizeLine);
            write(1,"\n",1);
            flag = 1;
            break;
         }
         else
         {
            r = readln1(fdin1,buf1,1024);
            s = readln1(fdin2,buf2,1024);
         }
      }

      nLine++;
   }