Totally new to C++, can't seem to get this simple code to work?

[nahla]

#include <iostream>

int main() */
{ double radius = 11; /* centimeters;
double pi = 3.14
double sphere_volume = (4/3)*pi*(radius * radius * radius);
double surface_area = 5 * pi * radius;
cout << "Volume = " << sphere_volume;
cout << "Area = " << surface_area;
return 0;
}


I have some error telling me about my int main(), I do not know what it means, I found this code and am just trying to fix it up for practice. Can someone show me how to fix it? I hate getting stuck

[zb0S216C]

The comment on the second line begins, but it does not end. You need a corresponding "*/" to complete the comment block. Otherwise, all subsequent code is considered a comment, including the closing brace of
"main( )" -- without the closing brace, "main( )" is not complete.

_Wazzak

[maeriden]

{ double radius = 11; /* centimeters

/* is a box comment, not a line comment. If you don't close it you're commenting out all the rest of your code

[nahla]

Does this fix the code? I'm am not at a school computer in linux to compile and see.

[maeriden]

EDIT: the "*/" at the end of the code is automatically written by the site, I don't know how to remove it

int main() */
{ double radius = 11; /* centimeters;
double pi = 3.14
double sphere_volume = (4/3)*pi*(radius * radius * radius);
double surface_area = 5 * pi * radius;
cout << "Volume = " << sphere_volume;
cout << "Area = " << surface_area;
return 0;
} */

Line 1: you have a close-comment that will throw an error
Line 2: you need to close that box comment. Just move the one from line one after "centimeters". Also, the semicolon is not needed since a comment is not an instruction
Line 3: missing ;
Line 4: (4/3) will evaluate to 1, because you're dividing two integers. Just writing 4.0/3.0 will suffice to evaluate them as floats
Line 6-7: just using cout will throw an error. You can:
- Write "std::cout" every time you need to use it. This is what I personally prefer
- Put "using namespace std;" before your main. Tip for the future: never do this in header files, it's bad practice
- Put "using std::cout;" before your main. This will allow you to avoid writing std:: before cout, but ONLY before cout. Avoid in headers

Little note: as of now the output to the console will be (random numbers)

Volume = 1986Area = 454

It will look nicer if you write

cout << "Volume = " << sphere_volume << std::endl;
cout << "Area = " << surface_area << std::endl;

You can see std::endl as the C++ way to put '\n' in strings

[Blue Shell]

#include <iostream>
using namespace std;
int main() 
{ 
const float pi = 3.14;
float centimeters, radius = 11, sphere_volume = (4/3)*pi*(radius*radius*radius), surface_area = 5*pi*radius;
cout << "Volume = " << sphere_volume <<endl;
cout << "Area = " << surface_area <<endl;
cin.get ();
return 0;
}

This should perform correctly. Your idea behind your program was good, and you only had syntax errors. I didn't see totally wrong, but so you remember not to do them again, here they are.

1) comment syntax is /* comment */ anything between the slash and star are discarded by the compiler. this is a block comment.
2) You need to the line "using namespace std;" after the header file <iostream>. this tells the compiler that you are using the standard input and output procedures.
3) You have forgotten some ";". They tell the compiler that the statement is over. This is extremely important, and the most common error, and I do it too xD.

Other then that, you did excellent.
I added a couple things to spice up your program.

You can do multiple declarations by separating your variables with commas.
Ex. type var1, var2, var3;
int weight, height;
You can also initialize the variables by separating them with commas too.
ex. type var1 = 0, var 2 =1, var3 = 999;
int height = 62, weight = 90;
At the end of your cout <<""; statement you may have noticed the <<endl; This just gives a new line to the console.
cin.get (); is a function you use with strings, but without any parameters, it just waits for a key to be pressed.
Good work, keep it up.

maeriden has the same point, and since he has more experience, take advice from him! xD

[TheIdeasMan]

Did anyone mention to the OP about line comments?

double radius = 11; // centimeters

The // starts the comment & it continues until the end of the line.

If you include the math header, then you can use M_PI directly, rather than declaring your own value for pi.

Edit:

I prefer to declare variables on there own line, so you can comment their meaning or other info like units or range etc.

[nahla]

Thank you guys so much, each of you made it super clear for me, now I have the right code and understand it much better!

[Blue Shell]

Glad to help, anytime.

[chipp]

learn more about syntax and C++ basics too :)