radius of a star help writing program, need corrections?

[Daleio]

hey im suppose to write a program using pelles C for windows to calculate the radius of the star using the formulas:

r = 1/2T^2 *sqrt( L/pi*σ)

L= 3.36192 *10^(140 - 2M/5)

σ = 5.67051*10^ -8

you are given and suppose to input the values for T and M to solve for r, so far I have this but im stuck and I dont even know if this is right:

#include <stdio.h>
#include <math.h>
 
int main (void)
{
    double r, T, M;
    // Read input data
    printf("\nr = ");
    scanf("%1f", &r);
    printf("T= ");
    scanf("&1f", &T);
    printf("M=");
    scanf("%1f", &M);
 
    //Perform calculation
    r = ((1/2T^2)*(sqrt(3.36192*10^(140-2M/5)/(pi*5.67051*10^-8));
            T=.................;
            M=................;
 
            //Display output
            printf("..............");
            return 0;
        }
 

any help would be greatly appreciated, thanks.

[sicarie]

Comments in code:

#include <stdio.h>
#include <math.h>
// i would recommend declaring pi here as a global (as pi's value is not going to change), you don't declare it anywhere, you just use it
 
int main (void)
{
    double r, T, M; 
    // Read input data
    printf("\nr = ");
    scanf("%1f", &r);
    printf("T= ");
    scanf("&1f", &T);
    printf("M=");
    scanf("%1f", &M);
 
    //Perform calculation
    r = ((1/2T^2)*(sqrt(3.36192*10^(140-2M/5)/(pi*5.67051*10^-8));
    // at 2T you need to change this to (1/2)*T and figure out if you want all of that squared, or just T
    // and it is the same thing with 'M'
   // and, of course, declare pi
   // and you're missing one more pair of parentheses at the end
//            T=.................;
//            M=................;
 
            //Display output
            printf("..............");
            return 0;
        }
 

Try making those changes and see if it compiles, then re-post your code, and we can work on the rest!

[Daleio]

Comments in code:

#include <stdio.h>
#include <math.h>
// i would recommend declaring pi here as a global (as pi's value is not going to change), you don't declare it anywhere, you just use it
 
int main (void)
{
    double r, T, M; 
    // Read input data
    printf("\nr = ");
    scanf("%1f", &r);
    printf("T= ");
    scanf("&1f", &T);
    printf("M=");
    scanf("%1f", &M);
 
    //Perform calculation
    r = ((1/2T^2)*(sqrt(3.36192*10^(140-2M/5)/(pi*5.67051*10^-8));
    // at 2T you need to change this to (1/2)*T and figure out if you want all of that squared, or just T
    // and it is the same thing with 'M'
   // and, of course, declare pi
   // and you're missing one more pair of parentheses at the end
//            T=.................;
//            M=................;
 
            //Display output
            printf("..............");
            return 0;
        }
 

Try making those changes and see if it compiles, then re-post your code, and we can work on the rest!

I was kind of wondering how to put unknown variables into the program. I am given values for T and M and somehow im suppose to put them into the program to solve for r. Im not quite sure how to put the equations in the program. I am suppose to put in the values of T and M to solve for r. This is my main problem. Please Help.

[sicarie]

I was kind of wondering how to put unknown variables into the program. I am given values for T and M and somehow im suppose to put them into the program to solve for r. Im not quite sure how to put the equations in the program. I am suppose to put in the values of T and M to solve for r. This is my main problem. Please Help.

If I understand you correctly, you either have a user inputting the variables, or you have a file with those variables, correct? (and which one?)

This is a page that details many different options you can use to get input from both the user and from a file (though you might have to do a little more digging if it is in a file - you can google "c read input from file" and you should get something, or you can post back here if you can't find anything).

Do those look like what you're trying to do, or did I miss what you were saying?

[Daleio]

these are the errors i get after i think i made all the corrections....

#include <stdio.h>
#include <math.h>

int main (void)
{
double r, T, M,pi;
// Read input data
printf("\nr = ");
scanf("%1f", &r);
printf("T= ");
scanf("&1f", &T);
printf("M=");
scanf("%1f", &M);

//Perform calculation
r = ((1/2*T^2)*(sqrt(3.36192*10^(140-2*M/5)/(pi*5.67051*10^-8)));
T=.................;
M=................;

//Display output
printf("..............");
return 0;
}




C:\Documents and Settings\......\Assign 2\radius.c(16): error #2168: Operands of ^ have incompatible types 'double' and 'int'.
C:\Documents and Settings\.....\Assign 2\radius.c(16): error #2168: Operands of ^ have incompatible types 'double' and 'int'.
C:\Documents and Settings\......\Assign 2\radius.c(16): error #2168: Operands of ^ have incompatible types 'double' and 'double'.
C:\Documents and Settings\......\Assign 2\radius.c(16): error #2001: Syntax error: found ';' - expecting ')'.
C:\Documents and Settings\........\Assign 2\radius.c(17): error #2039: Illegal expression.
C:\Documents and Settings\......\Assign 2\radius.c(17): error #2001: Syntax error: found '...' - expecting ';'.
C:\Documents and Settings\.......\Assign 2\radius.c(17): error #2061: Illegal statement termination.
C:\Documents and Settings\......\Assign 2\radius.c(18): error #2039: Illegal expression.
C:\Documents and Settings\........\Assign 2\radius.c(18): error #2001: Syntax error: found '...' - expecting ';'.
C:\Documents and Settings\.........\Assign 2\radius.c(18): error #2061: Illegal statement termination.
*** Error code: 1 ***

need help with these errors please. sorry im a newbie to programming

[hirak1984]

make the return type of main to void.

 void main();

and not

int main(void)

may be this will help

these are the errors i get after i think i made all the corrections....

#include <stdio.h>
#include <math.h>

int main (void)
{
double r, T, M,pi;
// Read input data
printf("\nr = ");
scanf("%1f", &r);
printf("T= ");
scanf("&1f", &T);
printf("M=");
scanf("%1f", &M);

//Perform calculation
r = ((1/2*T^2)*(sqrt(3.36192*10^(140-2*M/5)/(pi*5.67051*10^-8)));
T=.................;
M=................;

//Display output
printf("..............");
return 0;
}




C:\Documents and Settings\......\Assign 2\radius.c(16): error #2168: Operands of ^ have incompatible types 'double' and 'int'.
C:\Documents and Settings\.....\Assign 2\radius.c(16): error #2168: Operands of ^ have incompatible types 'double' and 'int'.
C:\Documents and Settings\......\Assign 2\radius.c(16): error #2168: Operands of ^ have incompatible types 'double' and 'double'.
C:\Documents and Settings\......\Assign 2\radius.c(16): error #2001: Syntax error: found ';' - expecting ')'.
C:\Documents and Settings\........\Assign 2\radius.c(17): error #2039: Illegal expression.
C:\Documents and Settings\......\Assign 2\radius.c(17): error #2001: Syntax error: found '...' - expecting ';'.
C:\Documents and Settings\.......\Assign 2\radius.c(17): error #2061: Illegal statement termination.
C:\Documents and Settings\......\Assign 2\radius.c(18): error #2039: Illegal expression.
C:\Documents and Settings\........\Assign 2\radius.c(18): error #2001: Syntax error: found '...' - expecting ';'.
C:\Documents and Settings\.........\Assign 2\radius.c(18): error #2061: Illegal statement termination.
*** Error code: 1 ***

need help with these errors please. sorry im a newbie to programming

[sicarie]

If you are going to do that, you need to remove the 'return 0;' at the bottom, otherwise you will get an error with main().

[sicarie]

If you look at the error messages, everything your compiler is complaining about is on lines 16, 17, and 18.

You can delete 17 and 18, as far as I can tell, you don't need them.

Then on 16, you need to be careful on what you are multiplying to what and how:

r = (( 1/2 * T^2) * (sqrt(3.36192 * 10^(140 - 2 * M/5) / (pi * 5.67051 * 10^-8)));

I think you should break that part up into several different sections - it will be easier for you and the compiler.

[Daleio]

yeah tahnks i got most of the problem worked out the only error i get now after th enew code....

#include <stdio.h>
#include <math.h>

int main (void)
{
double r, T, M,pi, z,a,b;
// Read input data
printf("\nr = ");
scanf("%1f", &r);
printf("T= ");
scanf("&1f", &T);
printf("M=");
scanf("%1f", &M);

//Perform calculation
r = ((1/2*z)*(sqrt(3.36192*a)/(pi*5.67051*b)));
z= pow(T,2);
a= pow(10,(140-2*M/5);
b=pow(10,-8);


//Display output
printf("..............");
return 0;
}


C:\Documents and Settings\.....\Assign 2\radius.c(18): error #2001: Syntax error: found ';' - expecting ')'.

[sicarie]

Actually, it looks pretty correct except that you need a ')' at the end of the statement, and you should change T^2 to pow(T,2) - that will return a double (while using the carat returns an int - which was what your compiler was saying).

(I'd still break it up, but that's just me - it looks very crammed to have all that in there on one line - I'm betting there will be a logic error in there somewhere...)

[Daleio]

nevermind i fix taht but get new error...

#include <stdio.h>
#include <math.h>
 
int main (void)
{
    double r, T, M,pi, z,a,b;
    // Read input data
    printf("\nr = ");
    scanf("%1f", &r);
    printf("T= ");
    scanf("&1f", &T);
    printf("M=");
    scanf("%1f", &M);
 
    //Perform calculation
    r = ((1/2*z)*(sqrt(3.36192*a)/(pi*5.67051*b)));
        z= pow(T,2);
        a= pow(10,(140-2*M/5));
        b=pow(10,-8);
 
 
    //Display output
            printf("..............");
            return 0;
        }
 

C:\Documents and Settings\........\Assign 2\radius.c(6): warning #2115: Local 'z' is initialized but never used.
C:\Documents and Settings\........\Assign 2\radius.c(6): warning #2116: Local 'pi' is used but never assigned a value.

[sicarie]

nevermind i fix taht but get new error...

#include <stdio.h>
#include <math.h>
 
int main (void)
{
    double r, T, M,pi, z,a,b;
    // Read input data
    printf("\nr = ");
    scanf("%1f", &r);
    printf("T= ");
    scanf("&1f", &T);
    printf("M=");
    scanf("%1f", &M);
 
    //Perform calculation
    r = ((1/2*z)*(sqrt(3.36192*a)/(pi*5.67051*b)));
        z= pow(T,2);
        a= pow(10,(140-2*M/5));
        b=pow(10,-8);
 
 
    //Display output
            printf("..............");
            return 0;
        }
 

C:\Documents and Settings\........\Assign 2\radius.c(6): warning #2115: Local 'z' is initialized but never used.
C:\Documents and Settings\........\Assign 2\radius.c(6): warning #2116: Local 'pi' is used but never assigned a value.

So the first is telling you that you declared z, assigned a value to it, but then didn't use it again. I'm betting that you wanted T-squared in your answer somewhere there ;).

The second is saying that you declared pi, but you never assigned it the value of pi. My suggestion was for a global, so that would be like this:

#include //...
#define PI    3.1415926
int main() 
// ...
 

Then whenever you use PI, it will have the value of 3.1415926.

[sicarie]

A side note that would otherwise lead to a logic error:

You declare the variables, but then go on to define them after you use them in a function. In C (and C++), when you define variables and do not give them values, they are initalized with whatever leftover values were in the memory allocated to them before they got there. This also known as 'junk' (was going to use a less-nice word there, but decided not to. You get the picture). Junk variables are hard to catch because they actually have a value, just not the one you think they do!

So I made some slight modifications below.

#include <stdio.h>
#include <math.h>
#define PI = 3.141592653
 
int main ( )
{
    double r, T, M, z,a,b;
    // Read input data
    printf("\nr = ");
    scanf("%1f", &r);
    printf("T= ");
    scanf("&1f", &T);
    printf("M=");
    scanf("%1f", &M);
 
    //this change in order should help properly perform the calculation
        z= pow(T,2);
    a= pow(10,(140-2*M/5));
    b=pow(10,-8);
    r = ((1/2*z)*(sqrt(3.36192*a)/(pi*5.67051*b)));
 
    //Display output
    printf("%d",r);
    return 0;
}
 

[Daleio]

i got the pi to work but i did use z in my r = equation right after the 1/2 i dont know why it says i dont use it the b and a work fine though

[Daleio]

#include <stdio.h>
#include <math.h>
#define pi 3.1415926

int main (void)
{
double r, T, M, z,a,b;
// Read input data
printf("\nr = ");
scanf("%1f", &r);
printf("T= ");
scanf("&1f", &T);
printf("M=");
scanf("%1f", &M);

//Perform calculation

z= pow(T,2);
a= pow(10,(140-2*M/5));
b=pow(10,-8);
r = ((1/2*z)*(sqrt(3.36192*a)/(pi*5.67051*b)));




//Display output
printf("The Radius is:");
return 0;
}

[sicarie]

i got the pi to work but i did use z in my r = equation right after the 1/2 i dont know why it says i dont use it the b and a work fine though

That is weird. Is it still throwing the error? (I literally JUST re-installed this computer anyway, and don't yet have any other programs installed, so I don't ahve a C compiler in front of me - sorry!)

[Daleio]

thats ok thanks anyway you helped me out a lot

[sicarie]

thats ok thanks anyway you helped me out a lot

Anytime! And be careful about that r= statement - I believe that the * has precedence over / . (Which means 1/2*z might end up being (1 / (2 * z ))!)

Definitely let me know if you figure out that 'z' statement - I'll look at it tomorrow when I get back to work.

[Daleio]

i think the problem is that in the z= statement i use T but T is an unknown. Is there a way to a T= statement if T is a number i want to input into the program

[sicarie]

i think the problem is that in the z= statement i use T but T is an unknown. Is there a way to a T= statement if T is a number i want to input into the program

But it looks like you input that with the scanf, and it should have given that warning about M as well...

Anyway, it's bedtime for me - I will look at it tomorrow, let me know if you figure it out!

[sicarie]

But it looks like you input that with the scanf, and it should have given that warning about M as well...

Anyway, it's bedtime for me - I will look at it tomorrow, let me know if you figure it out!

I think that is it, actually. If you look at the scanf - you use an & ampersand when in the rest you use a % percent. Try changing that!

[Daleio]

changed it but still get the same error

[Daleio]

hey I worked all the problems out but I dont get an answer, do you know what I did wrong, here is my updated code:


#include <stdio.h>
#include <math.h>
#define pi 3.1415926

int main (void)
{
double r, T, M;
// Read input data
printf("T= ");
scanf("%lf", &T);
printf("\nM=");
scanf("%lf", &M);

//Perform calculation


r = ((1/2)* pow(T,2))*(sqrt(3.36192*pow(10,(140-2*M/5)))/(pi*5.67051*pow(10,-8)));




//Display output
printf("The Radius is: ",r);
return 0;
}

[sicarie]

hey I worked all the problems out but I dont get an answer, do you know what I did wrong, here is my updated code:


#include <stdio.h>
#include <math.h>
#define pi 3.1415926

int main (void)
{
double r, T, M;
// Read input data
printf("T= ");
scanf("%lf", &T);
printf("\nM=");
scanf("%lf", &M);

//Perform calculation


r = ((1/2)* pow(T,2))*(sqrt(3.36192*pow(10,(140-2*M/5)))/(pi*5.67051*pow(10,-8)));




//Display output
printf("The Radius is: ",r);
return 0;
}

Printf() requires you to insert a representation of the variable in the output where you want it to show up. To represent a variable, you use the percent sign %, and 'lf' for a double.

Printf("the radius is: %lf", r);
 

[Daleio]

Ok I get a number now but whatever number i put in for T and M i only get the answer 0.0000. Is there some reason why th eprogram is not performing the calculation right.

[sicarie]

Ok I get a number now but whatever number i put in for T and M i only get the answer 0.0000. Is there some reason why th eprogram is not performing the calculation right.

(My C compiler is installing right now...) I think it's probably something in that r= statement. Can you go through and put parentheses around the individual actions?

For instance, part if it is (1/2*T^2) - should it be ((1/2)*(T^2))? or another way? There are all sorts of operator precedence rules in compilers, and that's why I was trying to get you to shorten this...

[Daleio]

hey i broke it up even more but still dont get right answer, heres the new code do you see anything wrong with it......


#include <stdio.h>
#include <math.h>
#define pi 3.1415926

int main (void)
{
double r, T, M, L,a,b,c;
// Read input data
printf("T= ");
scanf("%lf", &T);
printf("\nM=");
scanf("%lf", &M);

//Perform calculation


r = a*(sqrt(L/b));
L= 3.36192*pow(10,c);
a= 1/(2*pow(T,2));
b=pi*(5.67051*pow(10,-8));
c=(140-2*M)/5;



//Display output
printf("\nThe Radius is: %lf\n",&r);
return 0;
}

[Daleio]

I think the problems is because the values i out in for M and T do not register and are not being used because no matter what numbers i put in for them the answer is always the same. Is there something i have to do to tell the program that the values i enter are for T and M

[sicarie]

I think the problems is because the values i out in for M and T do not register and are not being used because no matter what numbers i put in for them the answer is always the same. Is there something i have to do to tell the program that the values i enter are for T and M

That should already be in place with the scanf's.

In each one, you get a double with the %lf, and then you tell it to be in the value of T and M with the &. You can try it without the ampersands, see if that makes a difference, but I believe those are right.

(stupid ubuntu doesn't install gcc! I'm really annoyed at them, and stumped, I thought the full install came with it, but I dont' have it!)