Basic file reading code with many comments

readfromfile_reallybasic.c

/*This program will read characters from a file, and for each line:
* print it, followed by the count of the characters in that line.*/

    #include <stdio.h>

    int main(void)
    {
        char filename[]="testinputfile.txt";
        
        /*This is a pointer that will point to the file (a single point in the file, not a whole line).
        It does not point to anything yet.*/
        FILE    *file_pointer; 

        char c; /*This will hold the character we read from the file.*/
        int counter=0; /*This will hold the number which we will increment each time we read a character that is not \n or EOF.*/
        
        file_pointer = fopen (filename, "r"); /* Now the file_pointer should point to something.*/
        if (file_pointer == NULL) /*If the pointer does not point to the file, do NOT try to process anything, but exit safely.*/
        {
            fputs ("Failed to open file.\n", stderr);
            return 1;
        }
        else /* The file_pointer now does point to the start of the file. */
        {
            /* The do-while, does not check the exit condition until the end of the iteration.
             * Therefore the last character fget will get from the file will be the EOF,
             * which we do not want to print either.*/
            do
            {
                c = fgetc(file_pointer); /* Get a character from where the file_pointer is pointing. */

                /* If this character is not the EOF, print the character.
                 * This will ensure the newlines from the file will be printed like before, 
                 * but does not try to print the EOF. */
                if (c != EOF)
                {
                    printf("%c", c);
                }

                /* If this character is both neither a '\n' (new line) nor an EOF, increment the counter,
                 * as we do not want the newline to be counted in the counter variable.*/
                if (c != '\n' && c != EOF)
                {
                    counter++;
                }
                /* Otherwise if the character is a new line, print then zero the counter variable.*/
                else if (c == '\n')
                {
                    printf("%i\n", counter);
                    counter=0;
                }
                /* As the last line may not end in a newline, but instead an EOF we check for it and a non-zero counter.
                 * As there is no newline preceding the EOF in this test, we will need to print an extra one before the number, if there /is/ a number.
                 * If number is zero, the last valid line was already processed and we do not print anything now.*/
                else if (c == EOF && counter!=0)
                {
                    printf("\n%i\n", counter);
                    counter=0;
                }
                
            }
            while (c != EOF);
        }
        fclose(file_pointer);

        return 0;
    }