Structing with grades

Im working on a program that is supposed to return a class average using a struct. I've found some examples that get me in the right direction, but at the moment, Im not getting very far in understanding how to format data/read data from a struct into my program and produce the result. I've got one example of temp data but no earthly idea or reference in how to make this work. At this point I would rather just have the information(data) in the program itself and not worry about reading from a text file or input from the screen. My code is still not where it needs to be, but I dont think I can go further until I know how to put the data into my program and understand the struct concept better. The rough code I'm working with so far is:

Code:

//MAIN.C
#include "cl_info.h"

int main(void)
{
	struct student temp, class[CLASS_SIZE]; // ????
	char grade;
	// Database for grades goes here?
	temp.grade = 'B';
	temp.last_name = "Jones";
	temp.student_id = 31223;

	//prints out each student#, student last name and letter grade
	printf("GRADE REPORT FOR STUDENT #: %d LAST NAME:
 %c FINAL GRADE: %
c\n",temp.student_id,temp.last_name,temp.grade);
	avg = average(struct student class[CLASS_SIZE]);
	//Assigns a letter grade for GPA
	if(avg > 4.0)
		printf("ERROR, TOO HIGH.  Check your logic!");
	if(avg == 4.0)
		grade = 'A';
	if(avg >= 3.0 && avg <= 3.99)
		grade = 'B';
	if(avg >= 2.0 && avg <= 2.99)
		grade = 'C';
	if(avg >= 1.0 && avg <= 1.99)
		grade = 'D';
	if(avg < .099 && avg >= 0)
		grade = 'F';
	if(avg <= -.001)
		printf("ERROR  TOO LOW.  Check your logic!");
			

	printf("The class grade average is a %c, or %f.3, 
based on a GPA scale of 4.0",grade,avg);
 //prints out the class gpa average and letter grade

	

return 0;

}

//CL_INFO.H

#include <stdio.h>

#define CLASS_SIZE 100

int average(struct student class[]);

struct student
{
	char	*last_name;
	int		student_id;
	char	grade;
};
float avg;

//AVERAGE.C

// Average's Class Grades

// 4 is for A, 3 for B...etc

#include "cl_info.h"

int average(struct student class[])
{
int i, a, result, tmp = 0, cnt = 0;

for(i = 0; i < CLASS_SIZE; ++i)
	{
	++cnt; //Brings count to 1.  This counter will be used to find the average
	a = class[i].grade; //Adds the first array to result
	result = tmp + a; // temp Sum of 2 students
	tmp = result;	// transfers the sum to temp for summing in the next iteration
	}
	
	avg = tmp / cnt; // class average (GPA)
	return avg; // returns class average to main
}

First off, you have alot of if statements in there that should be else ifs in the same statement. It's not possible for a value to have two different letter grades, is it? It's a logical error to use minimum in maximum in an if statement.

Instead of this:

Code:

	if(avg > 4.0)
		printf("ERROR, TOO HIGH.  Check your logic!");
	if(avg == 4.0)
		grade = 'A';
	if(avg >= 3.0 && avg <= 3.99)
		grade = 'B';
	if(avg >= 2.0 && avg <= 2.99)
		grade = 'C';
	if(avg >= 1.0 && avg <= 1.99)
		grade = 'D';
	if(avg < .099 && avg >= 0)
		grade = 'F';
	if(avg <= -.001)
		printf("ERROR  TOO LOW.  Check your logic!");

Consider doing this:

Code:

	
    if (avg > 4.0)
       printf("Check your logic.");
    else if (avg == 4.0)
       grade = 'A';
    else if (avg >= 3.0)
       grade = 'B';
    else if (avg >= 2.0)
       grade = 'C';
    else if (avg >= 1.0)
       grade = 'D';
    else if (avg >= 0.0)
       grade = 'F';
    else
       printf("Check your logic.");

It gives you the same results and it's much more quicker and logical.

Secondly, you should be reading in a outputting a string for the last name, not a character. Change "%c" to "%s".

Next, you have a syntax error on how you're setting float precision. It should be "%.2f" not "%f.2"