problem with functions & for loop !

Hi
I'm trying to write a code that will a print a table of results
the values of first column are known so I put them using for loop
then i tried calling functions inside the loop to calculate the value fot the other columns
the problem is that the third function depends on the value of the first & second functions but the values can not be sent there !
here is the code

Code:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define PI 3.141592653589793238462
 
void get_values(double *, double*);
void get_capacitance(double*, int, double);
void get_inductance(double*, int, double);
void get_attenuation(double,int, double, double);
void get_attdb(double);
 
int main(void)
{
   double inductor, capacitor;
   int F;
   double capacitance, inductance, attenuation, attdb;
 
        
   get_values(&inductor, &capacitor);
  
   printf("L = %lf, C = %lf\n", inductor, capacitor);
  
   for (F=100;F<=1000;F=F+100)
   {
       printf("%i",F);
       printf("\t");
      
       get_capacitance(&capacitance,F,capacitor);
       printf("%lf", capacitance);
       printf("\t");
      
       get_inductance(&inductance,F,inductor);
       printf("%lf", inductance);
       printf("\t");
      
       get_attenuation(attenuation,F, inductance, capacitance);
       printf("%lf", attenuation);
       printf("\t");
      
       get_attdb(attenuation);
       printf("\t");
      
       printf("\n");
   }   
   system("PAUSE");
   return 0;
}
 
 
void get_values(double *L, double *C)
{
   printf( "Please, enter the required inductor value");
   scanf("%lf", L);
        
   printf("Please, enter the required capacitor value");
   scanf("%lf", C);         
}
 
 
void get_capacitance(double *capacitance, int frequency, double C)
{
    *capacitance =(((1/(2 * PI * frequency * C))));
   
}
 
void get_inductance(double *inductance, int frequency, double L)
{
    *inductance = (2 * PI * frequency * L);
}
 
void get_attenuation(double attenuation,int F, double L, double C)
{
     attenuation = (1/(1-(2*PI*F*2*PI*F*L*C)));
 
}
 
void get_attdb(double att)
{
     printf("%lf",(20 * log10(att)));
 
}

thanks in advance

I think you mean to pass a pointer to the attenuation variable, rather than just the variable. Also, you never use attdb.

thanks for your reply TheBigH
I tried previously getting the capacitance & inductance values without using pointers but the same problem occured, when i send them to the attenuation functions i don't get the expected values.
i want to know how can i get the value from the function get_capacitance and send it to get_attenuation ?

No, you're right to use pointers to get the capacitance and inductance values. You should also use a pointer for the attenuation.

Passing just the variable to get_attenuation makes a copy of the variable which is discarded once the function ends. The changes you make to it are lost.

i tried it again but the same problem
the forth and fifth column values are not correct
here is the last code i tried

Code:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define PI 3.141592653589793238462

void get_values(double *, double*);
void get_capacitance(double*, int, double);
void get_inductance(double*, int, double);
void get_attenuation(double*,int, double, double);
void get_attdb(double*, double);



int main(void)
{
   double inductor, capacitor;
   int F;
   double capacitance, inductance, attenuation, attdb;

         
   get_values(&inductor, &capacitor);
   
   printf("L = %lf, C = %lf\n", inductor, capacitor);
   
   for (F=100;F<=1000;F=F+100)
   {
       printf("%i",F);
       printf("\t");
       
       get_capacitance(&capacitance,F,capacitor);
       printf("%lf", capacitance);
       printf("\t");
       
       get_inductance(&inductance,F,inductor);
       printf("%lf", inductance);
       printf("\t");
       
       get_attenuation(&attenuation,F, inductance, capacitance);
       printf("%lf", attenuation);
       printf("\t");
       
       get_attdb(&attdb, attenuation);
       printf("%lf", attdb);
       printf("\t");
       
       printf("\n");
   }    
   system("PAUSE");
   return 0;
}


void get_values(double *L, double *C)
{
   printf( "Please, enter the required inductor value"); 
   scanf("%lf", L);
         
   printf("Please, enter the required capacitor value");
   scanf("%lf", C);          
}


void get_capacitance(double *capacitance, int frequency, double C)
{
    *capacitance =(((1/(2 * PI * frequency * C))));
    
}

void get_inductance(double *inductance, int frequency, double L)
{
    *inductance = (2 * PI * frequency * L);
}

void get_attenuation(double *attenuation,int F, double L, double C)
{
     *attenuation = (1/(1-(2*PI*F*2*PI*F*L*C)));

}

void get_attdb(double *attdb, double att)
{
     *attdb =(20 * log10(att));

}

What values do you expect to get, and what are you getting?

first the user is asked to enter two values
the first should be 0.01
the second 0.000001
then you get results for five columns

frequency ____ inductance ____ capacitance ___ attenuation __ attenuation dB
100 _________ 6.283 _________ 1591.549 _____ 1.004 _______ 0.034
200 _________12.566 _________ 795.775 ______ 1.016 _______ 0.138
300 ________ 18.850__________ 530.517_______ 1.037_______ 0.314
etc

i'm getting for attenuation -0.000000 for all rows
and for attdB 1.#IND00

I think your formula for attenuation is wrong.

If I work it out by hand, using the values of inductance and capacitance from the program output, I get very small negative values for the attenuation.

it seems that was indded the problem because i treied simple formula and it worked
thank you very much for your help

No problem.