Thread: Cannot resolve error

I'm new in C programming and i have this assignment.

Prompts the user to enter the radius of the circle. A real number
is expected.

(b) Prints on the screen the circumference of the circle in the
following format:
“The circumference of a circle with radius x ft is equal to x.xx ft.”

(c) Prints on the screen the area of the circle in the following format:
“The area of a circle with radius x ft is equal to x.xx sq. ft.”

The results should be printed to a precision of 2 decimal digits.

Code:

#include<stdio.h>
void main()
{
int r;
int pi=3.14;
float cir,area;
printf("/n enter the radius of the circle");
scanf("%d",&r);
cir=2*pi*r;
area=pi*r*r;
printf("the circumference of the circle is%d", cir);
printf("the area of the circle is%d", area);
}

This is my code so far. It comes out with 2 errors on the last two lines. If someone could help me resolve these and get the program running that would be great.

Part of your problem is you are not using the proper format specifiers for your printf(). The %d specifier is the specifier for a int, not a float. Also in C an int does not contain any fractional parts, so 3.14 would actually be 3. And when you are doing math using int values they will not produce fractional parts. So if your radius is 1 cir would be 2*3*1= 6. and pi would be 3. I recommend that you change all your variables to float, or better yet double.

Jim

So if i changed all the variables to Double, how do i fix line 8 and lines 11 and 12?

Read the documentation for the functions you are using and use the proper format specifiers for the type. Here are a couple of links that may help: scanf() printf().

Jim

Alright i have all the variables sorted out, i have no errors now. But how do i get it to display 2 decimal places, i have rounded big numbers

Thanks everyone, i got everything resolved and done :]

Originally Posted by Babkockdood

Like Jim said, %d is used with integers. Use %f in the final two printf statements, since cir and area are of the type float.

Let's talk about pi now. First of all, 3.14 is not an integer. It is a float, like cir and area. Second of all, it's a constant. You don't need to set aside 4 bytes at run-time for a value that doesn't change. It would be more efficient to use

Code:

#define PI 3.14

at the top of your source file, before main() and after your #includes. This tells the compiler to replace every instance of "PI" with "3.14" before it compiles your code. Or you could use

Code:

const float pi = 3.14;

which essentially does the same thing. Note the "const" identifier.

EDIT: To print a float to only two decimal places, use %.2f instead of %f for your printf statements.