Student average program rookie in need of help

Need some baby steps to understand this structure bussiness. Here is my beginnings of code. I cant even make it past the compiler. My first struct statement says "missing code tag". whats wrong with the statement. I am working exactly the code as it is stated in the book and adding too , as instructed in the excercise. The statement struct is exactly like that in the book. So this is why i am confused to why i am getting a compile error.

The end game goal is to use the partial program in the book and build onto it making it calculate each students average.

thanks in advance for your help.

Code:

---

#include "class_info.h"
#include <stdio.h>

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);
    return 0;
}


void average(struct student class[])
{
    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);
}

---

here is my
class_info.h file

Code:

---

#include <stdio.h>


#define CLASS_SIZE  100

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

---

If you're using a C++ compiler it might complain about your usage of the variable name class.

What line is the error on? This one?

Code:

---

struct student          class[CLASS_SIZE];

---

You have extra semicolons here; get rid of them:

Code:

---

        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;

---

Code:

---

class[0].last_name = "Walker";

---

strcpy()...

Yes that is the line that is getting the error. I am using visio studio 2005 as my compiler.

So how do i fix it?

Quote:

---

Originally Posted by Mshock

Yes that is the line that is getting the error. I am using visio studio 2005 as my compiler.

So how do i fix it?

---

Be sure to set it to C not C++.

> class[0].last_name = "Walker";
> strcpy()...
No, the assignment is correct, it is a char* in the struct.

> int length = sizeof(class)/sizeof(student);
This only works when the array is in scope.
If all you have is a pointer to the array (what you get when you pass the array as a parameter), then this calculation does not do what you want it to.

Try
void average(struct student class[], int length)

And call it with
average( class, 10 );

> Yes that is the line that is getting the error
For the benefit of those who do not have your compiler, or can't be bothered to copy all your code to a project just to find out, say what your error messages are.

Okay how do i change the compiler in Visio Studio .net 2003 to use only the c compiler instead of C++. Or any alternate solutions to the error i get for the struct command with class.

Second questions is i added the two items metioned to the program here is the revised code. how does it look now.

Code:

---


#include "class_info.h"
#include <stdio.h>

int main(void)
{
  struct student          classs[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);
}

---

this is the error i get, sorry for not posting this earlier

(9): error C2332: 'class' : missing tag name
(9): warning C4094: untagged 'class' declared no symbols

Quote:

---

Originally Posted by Mshock

this is the error i get, sorry for not posting this earlier

(9): error C2332: 'class' : missing tag name
(9): warning C4094: untagged 'class' declared no symbols

---

As ive mentioned be sure to set it to C I bet this is a problem cause class keyword is reserved under C++.

been looking for where to change it in the program. So far dont see an option. Still looking

This is my output with gcc

Code:

---

rookie.c:1:24: class_info.h: No such file or directory
rookie.c: In function `main':
rookie.c:6: error: `CLASS_SIZE' undeclared (first use in this function)
rookie.c:6: error: (Each undeclared identifier is reported only once
rookie.c:6: error: for each function it appears in.)
rookie.c:9: error: `class' undeclared (first use in this function)
rookie.c:49: warning: implicit declaration of function `average'
rookie.c:6: warning: unused variable `classs'
rookie.c: At top level:
rookie.c:55: warning: `struct student' declared inside parameter list
rookie.c:55: warning: its scope is only this definition or declaration, which is probably not what you want
rookie.c:56: warning: type mismatch with previous implicit declaration
rookie.c:49: warning: previous implicit declaration of `average'
rookie.c:56: warning: `average' was previously implicitly declared to return `int'
rookie.c: In function `average':
rookie.c:59: warning: declaration of `length' shadows a parameter
rookie.c:59: error: `student' undeclared (first use in this function)
rookie.c:63: error: invalid use of undefined type `struct student'
rookie.c:63: error: dereferencing pointer to incomplete type
rookie.c:65: error: invalid use of undefined type `struct student'
rookie.c:65: error: dereferencing pointer to incomplete type
rookie.c:67: error: invalid use of undefined type `struct student'
rookie.c:67: error: dereferencing pointer to incomplete type
rookie.c:69: error: invalid use of undefined type `struct student'
rookie.c:69: error: dereferencing pointer to incomplete type
rookie.c:71: error: invalid use of undefined type `struct student'
rookie.c:71: error: dereferencing pointer to incomplete type
rookie.c:77:2: warning: no newline at end of file

---

Man just a tip, take smething like Dev-Cpp or MingW

Maragato, your gcc output is incorrect. Read the first line: "class_info.h: no such file..." Try saving the file (OP posts it above), and then list a compiler output. Such as this one: (I called his main file "ci.c" by the way... I'm a lazy typist...)) (gcc 3.4.2, MinGW)

Code:

---

ci.c: In function `main':
ci.c:9: error: `class' undeclared (first use in this function)
ci.c:9: error: (Each undeclared identifier is reported only once
ci.c:9: error: for each function it appears in.)
ci.c:49: warning: implicit declaration of function `average'
ci.c:6: warning: unused variable `classs'
ci.c: At top level:
ci.c:56: error: conflicting types for 'average'
ci.c:49: error: previous implicit declaration of 'average' was here
ci.c: In function `average':
ci.c:59: error: 'length' redeclared as different kind of symbol
ci.c:55: error: previous definition of 'length' was here
ci.c:59: error: `student' undeclared (first use in this function)

---

...which is hopefully a better represntation of the problem.

Reading that, in main(), you've got a variable called "classs" but not "class".
You never prototyped funtion average.
And finally, you have two length variables in average. (One which uses student, which isn't defined. If you're following the suggestions given, you probably want to remove the one involving student.)

Quote:

---

Originally Posted by Cactus_Hugger

Maragato, your gcc output is incorrect. Read the first line: "class_info.h: no such file..." Try saving the file (OP posts it above), and then list a compiler output. Such as this one: (I called his main file "ci.c" by the way... I'm a lazy typist...)) (gcc 3.4.2, MinGW)

Code:

---

ci.c: In function `main':
ci.c:9: error: `class' undeclared (first use in this function)
ci.c:9: error: (Each undeclared identifier is reported only once
ci.c:9: error: for each function it appears in.)
ci.c:49: warning: implicit declaration of function `average'
ci.c:6: warning: unused variable `classs'
ci.c: At top level:
ci.c:56: error: conflicting types for 'average'
ci.c:49: error: previous implicit declaration of 'average' was here
ci.c: In function `average':
ci.c:59: error: 'length' redeclared as different kind of symbol
ci.c:55: error: previous definition of 'length' was here
ci.c:59: error: `student' undeclared (first use in this function)

---

...which is hopefully a better represntation of the problem.

Reading that, in main(), you've got a variable called "classs" but not "class".
You never prototyped funtion average.
And finally, you have two length variables in average. (One which uses student, which isn't defined. If you're following the suggestions given, you probably want to remove the one involving student.)

---

Thanks by pointing the header mistake.

Oki man Ive re-writen and got a working copy take a look on the way you initialize your name field.
You also still programming in c++ cause you need typedef struct foo...

Maybe read the manual?
http://msdn.microsoft.com/library/de...c.2c_2f.Tp.asp

Thanks for the help with the switching the program over to C programing. Here are the final errors i am getting

(49): error C2143: syntax error : missing ';' before 'type'
(56): error C2449: found '{' at file scope (missing function header(77): error C2059: syntax error : '}'


After i get this function working I need to have the program print out the student average. Right now i am just trying to understand how to make this structure stuff work to just do the class average , goal is student average.

Am i even close to getting this thing running. Let me know your suggestions.

thanks in advance for your help

main.c

Code:

---

#include "class_info.h"
#include <stdio.h>

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;

        void 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)
}
return 0

---

here is my class_info.h file

Code:

---

#include <stdio.h>


#define CLASS_SIZE  100

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

---

Man look:

Code:

---

/*As I'm in GREAT MOOD I will code a bit for ya*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(void){
        char *foo;
        /*PAY ATTENTION*/
        char bar[] = "bar";
        char quux[20];       
        char *zyz;
       
        foo = bar;
        printf("Gimme input to quux :");
        scanf("%s",quux);
       
        printf("%s\n",foo);
        zyz = quux;

        printf("%s\n",zyz);
        strcpy(quux,foo);
        printf("%s\n",quux);

        return 0;
}

---

Then Ive compiled with:
gcc -W -Wall -Wbad-function-cast -Wcast-align -Wcast-qual -Wdisabled-optimization -Wendif-labels -Wfloat-equal -Wformat-literal -Winline -Wmissing-declarations -Wmissing-prototypes -Wnested-externs -Wno-unused-parameter -Wpointer-arith -Wshadow -Wstrict-prototypes -Wundef -Wwrite-strings -pedantic learn.c -o learn

No warnings.

I have your code doing the right thing but we want you to succed, you can't use an array as left value in C. So you need something like strcpy to read the names to the struct.
Hope it helps. Also I humbly recommend you to read http://pw1.netcom.com/~tjensen/ptr/pointers.htm .

I need some serious help. This is an excercise in the book suggested to do to learn the structure stuff. I am completely lost. The book was very limited. Actually one of the worst course books i have ever seen.

this excercise started off like this.

Using the student record example in Section 12.2, "Accessing a Member," on page 394, write a function that prints the average for each student in a class. Let an A grade have Value 4, a B grade have value 3, and so forth.

Here is all that page 394 has,, this whole chapter didnt explain very well. Ira pohl is a terrible c programing author.

In file Class_info.h

Code:

---

#Define CLASS_SIZE 100

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

---

in another file it has this:

Code:

---

#include "class_info.h"

int main(void)
{
struct student temp, class[CLASS_SIZE];
..........

---

then it says :

assign values to memebers

temp.grade = 'A'
temp.last_name = "Bushker";
temp.student_id = 590017;



That is all there is on 394, not even a complete description on what the hell is going on. I am also taking C++ it is so much easier than this C programing class.


I am working on my own with no instructor support. Can you please end the PAIN. Show me what to do and explain so i can understand structures.

Flame me if you will. But if a person is learning sometimes it is best to show an example of how to use it , rather than cryptic messages on what small changes you would do. I know the homework policy. THIS IS NOT HOMEWORK < NOR AN ASSIGNMENT TO TURN IN. This is merely an excercise suggested to do to understand structures.


Please help me.

Your code, as posted recently. Watch the comments

Code:

---

#include "class_info.h"
#include <stdio.h>

/*!! added prototype */
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;

  /*!! changed into a function call */
  average( class, 10 );

  return 0;
}


void average(struct student class[], int length) /*!! deleted ; */
{
  double sum=0.0,avg;
  int i;
  /*!! deleted - already passed as a parameter */
  /*!! 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);/*!! added ; */
}
/*!! deleted */
/*!! return 0 */

---

Salem thanks for the help to figure out class average. How would i go about figuring student averages?

Quote:

---

Originally Posted by Mshock

Salem thanks for the help to figure out class average. How would i go about figuring student averages?

---

Use what you learnt here, and modify it to suit your needs.

Well I still have no idea how to get each students average to printout. an A=4 , etc...

thanks for trying to help me. I have no clue. Even when i follow what people are saying it still makes no since. I need to see this program work with this sturcture stuff to understand all the higher level talking in this post.

Use the caveman stuff i started off with and keep it simple. I am still at a stand still in the structures chapter , and cant proceed to the next stuff without understanding this. People can type use strcpy etc... but i am serious the book is C by dissection by Ira pohl 4th edition. It is a horrible book for showing you anything in the excercises.

I realize you guys get upset with the please do it for me. Please read the homework stuff. I just want to see this thing from start to finish to understand structures.

You don't know how to find the average of something? Do you know how to average in basic math? The concept is the same. Sum all of the numbers, and divide by the total number of numbers. Do that for each student individually to get each average.


Quzah.

its the coding , not a matter of not understanding how to figure out averages of students grade.

Well what is it that you don't get about structs? You said that you
study C++ and C, so assuming that you've encountered classes,
structs are just much simpler, less powerful versions of them.
The idea is this: The basic data types are great and programmers
come up with all sorts of logical representations of real world data
using them, but its not always enough. Sometimes we want to
represent a type of data with multiple attributes - in C we use
structs to achieve representations of more complex "objects" (in
a manner of speaking). We create these structs from more basic
data types (int, char, float) and arrays of same as required (you
have character strings in yours).

The structs we write are essentially data types in their own right,
in that they can be thought of as ints or floats and what not,
except structs have separate parts (the attributes described
above) called members. In our programs, we declare instances of
ints, we can do the same with structs. We can even do arrays.

Lets take a look at your program:

Code:

---

int main(void)
{
  struct student class[CLASS_SIZE];

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

---

The first line is declaring an array of your struct type called
student, and calling it class. CLASS_SIZE is a constant you have
defined as 100. You declared an array of 100 "students", just
as you would do to declare 100 ints.

The next three lines perform assignment on the 0th element
of that array - setting the grade member to 'A', setting the
last_name char pointer to the string "Walker", and setting
the student_id to 590017. There you have a fully set up
struct, 99 to go!

It really doesn't get much clearer than this: the use of the '.'
means that we are accessing a specific member of the struct.
When a struct is passed by pointer to a function, the syntax for
accessing members changes to '->', but that's not important for
the current program.

Lastly, just to simplify the code segment above, we are looking
only at 1 element of the struct, so if we change the declaration
to a single variable, the small section of code above behaves as
follows:

Code:

---

int main(void)
{
  struct student students;

  students.grade = 'A';
  students.last_name = "Walker";
  students.student_id = 590017;

---

I'm only posting this to avoid any confusion with the use of an
array. From what i've seen, this is a terrible task to introduce
structs in a beggining C book - such books should take baby steps
with the topic since the idea can confuse people. Why do you
have to use that book if you recognise how bad it is?

Hope this clarifies things a bit - post questions if you have any
difficulty in understanding this post, feel free to come back and
ask questions.

Oh yeah, and about finding students average grade - you only
have one grade per student - at the moment, that's the average
grade - unless you implement features to add more grades to
each individual students record.

void averageForStudent(struct student class[], int length, char *studentName);

Coupled with
if ( strcmp( class[i].last_name, studentName ) == 0 )

Should be enough of a hint to at least try to write some kind of an answer.