read text file using c/c++

Do a getline, and then process the line you got. Since you want to split it up at fixed indexes, that shouldn't be too hard ... substr should help :

        http://www.cplusplus.com/reference/string/getline.html
        http://www.cplusplus.com/reference/string/string/substr.html

Don't forget to check out the example code at the bottom of those pages.

For reading a file, check out this tutorial :

        http://www.cplusplus.com/doc/tutorial/files.html

You could read 1 character at a time and loop through until you find what you want..

#include <cstring>
#include <fstream.h>
using namespace std;

string readCharacters(int charStart, int charEnd, char* filename)
{
   string ret;
   ifstream file (filename); // open file stream for reading using filename specified
   if ( !file.is_open() || !file.good() )
   {
      // Error has occured opening file: Handle it.
   }
   else
   }
      char c;
      for (int a = 0; a < charEnd; a++)
      {
         c = (char)file.get(); // Get the character at this point in file
         if ( a > charStart && a < charEnd ) // if the character
         {
            ret += c; // append character to string
         }
      }
   }
   file.close();
   return ret;
}

That is roughly how you could do it in C++, not sure if it works as I haven't tested it.
You would use this function to get characters from charStart to charEnd in the file specified by filename.. i.e.

string a = readCharacters(0,4,"C:\\file.txt");
string b = readCharacters(5,8,"C:\\file.txt");
etc

a simple program to read file line by line
        #include <stdio.h>
       #include <stdlib.h>

       int main(void)
       {
            FILE * fp;
            char * line = NULL;
            size_t len = 0;
            ssize_t read;
            fp = fopen("file.txt", "r");
            if (fp == NULL)
                 exit(EXIT_FAILURE);
            while ((read = getline(&line, &len, fp)) != -1) {
                 printf("Retrieved line of length %zu :\n", read);
                 printf("%s", line);
            }
            if (line)
                 free(line);
            return EXIT_SUCCESS;
       }