Call by value & call by reference in C [calc area and volume of a sphere]

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I have to write a sphere () function that calculates the area and volume of a sphere. The function receives three transfer parameters: the radius and two pointers to double variables, in which the function sphere () writes back the area and the volume of the sphere . The input and output takes place in main (). 

For a sphere with radius R the following applies: area = 4 * PI * R * R, volume = 4 * PI * R * R * R / 3

What I have tried:

So far I've come to that, its literally not much but i dont know how to slove it

C++

#include <stdio.h>
#define pi 3.14159
void sphere(double*, int*);

int main(void) {

    setvbuf(stdout, NULL, _IONBF, 0);
    setvbuf(stderr, NULL, _IONBF, 0);


  
    return 0;
}
void sphere() {
   
}

Posted 29-Jun-20 7:37am

R7TSN

Updated 29-Jun-20 9:32am

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OriginalGriff · Accepted Answer · 2020-06-29T09:01:00

Unless otherwise specified, all function parameters in C are passed by value, not reference - which means that a copy of objects is passed to the function, and changes to that copy will not affect the outside world.
If you think about it, that makes a lot of sense.
What if it was passed by reference?

C++

void foo(int bar)
   {
   bar = bar * 2;
   }
...
int x = 666;
foo(x);

would not cause any problems, and x would contain the new value.
But what happens if we do this?

void foo(int bar)
   {
   bar = bar * 2;
   }
...
foo(666);

Should the value of a constant be changed? That's not a good idea, not at all!

To tell C to pass by reference, you pass a pointer to the value:

void foo(int* bar)
   {
   *bar = *bar * 2;
   }
...
int x = 666;
foo(&x);

And the system will now not allow you to pass a constant, only a variable!

See here: Function call by reference in C - Tutorialspoint[^]

Rick York · Accepted Answer · 2020-06-29T09:32:00

Solution 2

I have very little to add to Mr. Griff's solution. Just a few details :

C++

#include <stdio.h>
#define _USE_MATH_DEFINES
#include <math.h>       // defines PI and various mathematical things

void sphere( double radius, double * pVolume, double * pArea )
{
}


int main(void)
{
    double radius = 2.5;
    double volume = 0;
    double area = 0;
 
    sphere( radius, & volume, & area );

    // output values

    return 0;
}

Posted 29-Jun-20 9:32am

Rick York

Comments

Rick York 29-Jun-20 21:15pm

Note : math.h defines the constants with a leading M_ prefix. Pi is M_PI.

CPallini 30-Jun-20 2:09am

5.

KarstenK 30-Jun-20 3:18am

using the term objects is misleading.

Rick York 30-Jun-20 12:35pm

I think Grif did, I did not.