Thread: c program help

Hello, I am trying to create a program that is supposed to calculate and print the average of several grades entered by the user.

The output is supposed to look something like this:
----------------------------------------------------------------------
This program calculates the average of as many grades you wish to enter.



First, enter the number of grades to process: 4


Now enter the 4 grades to be averaged.


Enter grade #1: 90
Enter grade #2: 80
Enter grade # 3: -20
*** Invalid entry. Grade must be 0 to 100. ***
Enter grade #3: 25
Enter grade #4: 54


The average of the 4 grades entered is 62


You have a letter grade of D-
----------------------------------------------------------------------

Here is what I have so far:
-----------------------------------------------------------------------

Code:

#include <stdio.h>
int main(void)
{

/* Output initial greeting and introduce program */
/* --------------------------------------------- */

printf ("This program caluculates the average of as many grades as you wish to enter.\n");

/* Declare variables. */

int number_of_grades, i, grade;
int grade_total = 0;
int invalid_entry = 0;
float average;
char letter_grade;
char grade_A, grade_AB, grade_B, grade_BC, grade_C, grade_CD, grade_D, grade_F;


/* Prompt user for number of grades to be entered. */
/* ------------------------------------------------*/

printf ("First, enter the number of grades to process: ");
scanf ("%i", &number_of_grades);

/* Output appropriate message based on number of grades entered. */
/*---------------------------------------------------------------*/

printf ("Now enter the %i grades to be averaged.\n", number_of_grades);

for (i = 1; i <= number_of_grades; i++)

{

/* Prompt user for grades. */
/* ----------------------- */

printf ("Enter grade #%i: ", i);
scanf ("%i",&grade);


/* If grade is out of range (less than zero, OR greater than
100), output error message, otherwise output grade entered.*/
/* ---------------------------------------------------------- */

if (grade > 100 || grade < 0)
{
printf ("*** Invaid entry. Grade must be 0 to 100. ***\n");
i --; 
}

else

{

/* Assign values */ 
/* --------------*/

grade_total = grade_total + grade; 
}

} // end for loop


/* Calculate average and display output */
/* ------------------------------------ */

average = (float) grade_total / number_of_grades;
printf("\nThe average of the %i grades entered is: %.0f", number_of_grades, average);

/* Assign values to letter grades */
/* -------------------------------*/

letter_grade = grade_total / number_of_grades;

if ( (char) average >= 93 && <= 100) 
{

printf ("You have a letter grade of %c\n", grade_A);

}

else ( (char) average <= 92 && >= 88)
}

printf ("You have a letter grade of %c\n", grade_AB); 

{
if ( (char) average <= 87 && >= 83)
}
printf (" You have a letter grade of \n", grade_B);

{

else ( (char) average <= 82 && >= 78)
}

printf ("You have a letter grade of\n, grade_BC");

{

if ( (char) average<= 77 && >= 73)

}
printf ("You have a letter grade of C\n");

{

else ( (char) average <= 72 && >= 68)

} 
printf ("You have a letter grade of\n", grade_CD);

{

if ( (char) average <= 67 && >= 63)

}
printf ("You have a letter grade of\n", grade_D);

{ 

else ( (char) average <= 62 && >= 0)

}
printf ("You have a letter grade of\n", grade_F);

{


} //end main

------------------------------------------------------------------------
The program isn't working and I can't figure out how to fix it. I am getting errors on lines 76,86,91,98,105,112,119,and 126. Any help would be much appreciated.