Thread: Why do variables equal functions?

That makes sense, but I guess I do not undestand what makes it tick completely.

In this program, I am lost. it is a similar situation, main can only call other functions, and the other frunctions perform the actions. What I cannot get to work is passing my variables from one function to another.

/*Determine a student's letter grade based on three input number grades,and calculating average and other factors */

#include <stdio.h>

void PrintHeading (void);
int GetScores (int);
float Average (float);
int GetGrade (char);
int PrintGrade (void);

int main (void)
{


GetScores();
Average(Score1, Score2, Score3);
GetGrade(Avg);
PrintGrade(Grade);

return 0;
}

int GetScores (void)
{
int Score1, Score2, Score3;

printf("Intput three scores, seperated by a space,then press [Enter].");
scanf("%d %d %d", &Score1, &Score2, &Score3);

return 0;
}

float Average (int Score1, int Score2, int Score3)
{
float Avg, Avg2;

Avg = (Score1 + Score2 + Score3)/3;
Avg2 = (Score2 + Score3)/2;

return Avg;
}

int GetGrade (float Avg, Avg2, int Score3)
{
char Grade;

if Avg >= 90
Grade = A
else if Avg >= 70 && Score3 > 90
Grade = A
else if Avg >= 70 && Score3 < 90
Grade = B
else if Avg >= 50 && Avg2 > 70
Grade = C
else if Avg >= 50 && Avg2 < 70
Grade = D
else Grade = F

return Grade;
}

int PrintGrade (char Grade)
{
printf ("The students grade is: %s", Grade);
}

Thanks, I understand the scope, but if I declare

int Score1, Score2, Score3 in main, then it tells me that I am not using the declared variables.

I am more worried about the other functions right now, I will debug GetGrade next, but I think that I can fix the issues with it.

I sense you haven't learned passsing by reference yet.
Here's something more manageable, I followed your semantics :


#include <stdio.h>

int score1, score2, score3;
char grade;
float avg, avg2;

void get_scores();
float average(int, int, int);
float average2(int, int);
char get_grade(float, float, int);
void print_grade(char);

int main (void)
{
get_scores();
avg = average(score1, score2, score3);
avg2 = average2(score1, score2);
grade = get_grade(avg, avg2, score3);
print_grade(grade);

return 0;
}

void get_scores(void)
{
printf("Intput three scores, seperated by a space, then press [Enter].");
scanf("%d %d %d", &score1, &score2, &score3);
}

float average(int score1, int score2, int score3)
{
return (score1 + score2 + score3) / 3.0;
}

float average2(int score2, int score3)
{
return (score2 + score3) / 2.0;
}

char get_grade(float avg, float avg2, int score3)
{
if (avg >= 90) return 'A';
else if (avg >= 70 && score3 > 90) return 'A';
else if (avg >= 70 && score3 < 90) return 'B';
else if (avg >= 50 && avg2 > 70) return 'C';
else if (avg >= 50 && avg2 < 70) return 'D';
else return 'F';
}

void print_grade (char grade)
{
printf ("The students grade is: %c", grade);
}

What I have a problem with is passign multiple variables. If it is just one, I am okay, but when it comes to passing two or three, I get compile errors.

I do not know when to actually declare the variable, as we have been told to NOT use global variables. Also, can you return more than one value, or just one?


Thanks, this is really helping me. I want to learn, and the explanations are great.

Originally posted by quzah
> I sense you haven't learned passsing by reference yet.

Passing by "reference" is NOT a feature in C. Again:

void myfunction( int &var );

This is NOT valid C code. This is C++ code. You have to use pointers if you want to emulate this behaviour.

Quzah.

While we are supposed to be using C, we build as .CPP, and compile as C++. (My professor has been programming in Cand C++ since their inception).

However, we are not using pass by reference, but we can use pointers or pass by value (pointers were briefly touched upon, not fully explained, but that is not the topic of this thread).

Originally posted by quzah
This is how you design a function so that it takes multiple values.
Remember that when you normally declare variables, you can do it all on the same line?

int x,y,z;
float a,b,c;

Well you can't do this in functions. You have to do them seperately:

void myfunction( int x, int y, int z, float a, float b, float c );

See how that is different? Ok, just pretend that the , operator in your function declaration is like the ; operator. What you have to do when declaring functions is seperate each new argument by a comma, and then, for the next new one, you have to give it a type and a variable name. (There are a few execptions to this, but for now, just go by what I said, and you should be ok.)

Quzah.

That makes sense. But how do I know where to initialize the variable in the first place? If I initialize it in main, then pass it to the called function, the value will be as set in main, right? So I would have to initialize it in the function that actually processes it, and uses another variable to return a value.

If I want to return more than one value, do I have to use a pointer? or is there an easier way?

Well if u initialialize a variable in main which u want to keep using and keep updating with the function then assign the return value of the function to it.

Lets say:

Code:

void main()
{
   int a=1;// a is 1 right now
 a=callfunction(a); //when calling the function a is stll 1;

 //now after the a is returned as 2 and assigned to 'a'. Now 'a' is 2

}
int callfunction(int a)
{
  a=2;
return a;
}

For your second question, seethis