Thread: gpa program not working

I am trying to complete an example in my book and I dont want to go any further until I complete it. It wants me write a function that prints the average for each student in a class and prints the class average. Let an A grade have Value 4, a B grade have value 3, and so forth. I have been pulling my hair out and I got t to print out the class average but I am lost as to how to get the student average. Here is the code:



in the .h file

Code:

#include <stdio.h>


#define CLASS_SIZE  100

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

in the .c file



#include "class_info.h"
#include <stdio.h>
void average(struct student     class[], int length);
int main(void)
{
   struct student           class[class_size];


    class[0].grade = 'A';
    class[0].last_name = "Walker";
    class[0].student_id = 590017;

    class[1].grade = 'B';
    class[1].last_name = "Smith";
    class[1].student_id = 590118;

    class[2].grade = 'C';
    class[2].last_name = "jones";
    class[2].student_id = 590219;

    class[3].grade = 'A';
    class[3].last_name = "Bubba";
    class[3].student_id = 590320;

    class[4].grade = 'B';
    class[4].last_name = "johns";
    class[4].student_id = 590421;

    class[5].grade = 'C';
    class[5].last_name = "Walker";
    class[5].student_id = 590017;

    class[6].grade = 'D';
    class[6].last_name = "Smith";
    class[6].student_id = 590118;

    class[7].grade = 'B';
    class[7].last_name = "jones";
    class[7].student_id = 590219;

    class[8].grade = 'A';
    class[8].last_name = "Bubba";
    class[8].student_id = 590320;

    class[9].grade = 'C';
    class[9].last_name = "johns";
    class[9].student_id = 590421;

	average( class, 10 );

    return 0;
}


void average(struct student     class[], int length)
{
    double sum=0.0,avg;
    int i;
//    int length = sizeof(class)/sizeof(student);

    for( i=0;i<length;++i )
    {
        if( class[i].grade == 'A' ) 
        sum+=4;
        if( class[i].grade == 'B' ) 
        sum+=3;
        if( class[i].grade == 'C' ) 
        sum+=2;
        if( class[i].grade == 'D' ) 
        sum+=1;
        if( class[i].grade == 'F' ) 
        sum+=0;

    }
    avg = (sum/length);
    printf("The average for the class is %f.\n", avg)
}

can someone lead me out of the darkness. It will print the class average now all i have to do is get it to print out the student and his average with a=4, b=3, c=2, d=1

Code:

void average(struct student     class[], int length)
{
    double sum=0.0,avg;
    int i;
//    int length = sizeof(class)/sizeof(student);

    for( i=0;i<length;++i )
    {
        if( class[i].grade == 'A' ) 
        sum+=4;
        if( class[i].grade == 'B' ) 
        sum+=3;
        if( class[i].grade == 'C' ) 
        sum+=2;
        if( class[i].grade == 'D' ) 
        sum+=1;
        if( class[i].grade == 'F' ) 
        sum+=0;

    }
    avg = (sum/length);
    printf("The average for the class is %f.\n", avg)
}

You need to simply loop through the array of structs, similar to what you did for the class grade average, above.

But no "If (class[i].grade ==...) this time. Now it's just:

Code:

for (i = 0; i < length; i++)  
   printf(" %s, %c", class[i].name, class[i].grade);

If you need to add more print statements, remember to add curly braces before and after the lines after the for (...), code line.

Also, note that CLASS_SIZE is not the same as class_size. Just a typo, maybe?

I cleaned it up and put that snippet of code in . It prints out the name and Grade like this
Walker A
Walker B
I need to add the grades of each student and divide them by the grades and show the average.
Can some one start me off?

Here are a few other things

Code:

for( i=0;i<length;++i )
    {
        if( class[i].grade == 'A' ) 
        sum+=4;
        if( class[i].grade == 'B' ) 
        sum+=3;
        if( class[i].grade == 'C' ) 
        sum+=2;
        if( class[i].grade == 'D' ) 
        sum+=1;
        if( class[i].grade == 'F' ) 
        sum+=0;

    }

If you are going to use the K&R style, then the for loop should be constructed as

Code:

for( i=0;i<length;++i ) {

}

As opposed to emulating the Pascal loops.

Code:

    printf("The average for the class is %f.\n", avg)

printf() is missing the semicolon.

Originally Posted by matthughes

I cleaned it up and put that snippet of code in . It prints out the name and Grade like this
Walker A
Walker B
I need to add the grades of each student and divide them by the grades and show the average.
Can some one start me off?

First thing I'd do is get rid of the duplicate student records, Bubba, Walker, etc. You might have two students with the same last (even first), names, but they shouldn't have the same student ID number! That will clear up some unneeded confusion.

To do what you want just add the curly braces I mentioned in the previous post around all the statements following the for () code line.

Then use a sum or total variable, to keep a sum of all the grades, using the A == 4,
B == 3, etc., method.

Code:

if (grade == 'A') sum += 4;
if (grade == 'B') sum += 3;

For all the grades. When you have finished the for loop, your sum will be ready to be divided by the number of students in the class. If you want something more accurate than integer division which cuts down to the next lowest integer, then make sum and student number, either floats or doubles, rather than integers. (You could also cast them, but I'm thinking that's something you haven't studied, yet.)

That will give you your average.

You'll need to add the print statement to show the new data (average, whatever), after the for loop.

I am so novice beginner that this is all I come up with

Code:

	for (i = 0; i < length; i++)
	{
		if(class[i].grade == 'A' && class[i].student_id == 1)
		total += 4, gradecnt +=1;
		if(class[i].grade == 'B' && class[i].student_id == 1)
		total += 3, gradecnt +=1;
		if(class[i].grade == 'C' && class[i].student_id == 1)
		total += 2, gradecnt +=1;
		if(class[i].grade == 'D' && class[i].student_id == 1)
		total += 1, gradecnt +=1;
		studavg = (total/gradecnt);
		next +1;
	}
		printf("The average for the Walker is %f.\n", studavg);

when i do this with the studavg it messes up all the other students can someone point out something better? than doing the if statement 16 times to test the grade and id ?

Wow thanks for explaining it like that the way I had it I couldnt sort the grades between students and the class average and the first one that pulled up would distort the averages of the other students

Glad you liked it, Matt. I'm very pleased with the program, now. (and I was scowling WTF when I saw how the data REALLY was arranged), for sure. I am not used to that!

That algorithm for StudentAverages() is one I'm going to have to keep in my "dark secret algo's" notebook. It handles that messy data, in good order, without needing sorting, or indexing.

The performance would not be good with huge amounts of data, but when was the last time you saw a class with tens of thousands of student grades?