Re: [Dev-C++] weird result

[Abhijit S. <mu...@gm...>]

int is, by default, signed, so one bit of your (signed) int variable (of
size 32 bits) is used to denote sign (+ve means 0, -ve means 1). 31 bits are
left, so, in effect, your int can hold from -((2**31) + 1) to +(2**31) where
** denotes exponentiation... in normal numbers, from -2147483648 to
+2147483647. The value of +2147483648 cannot be stored in the (signed) int.
It wraps around, and becomes the negative extreme. Dissect the bit-codes for
the numbers for more clarity.

The problem can be solved by using an unsigned int, which can hold a value
from 0 to +((2**32) - 1), i.e., 4294967295.

Changed code:
-----------------------------Start Code---------
#include <iostream>
#include <cstdlib>

using namespace std;
typedef unsigned int uint;

uint Power(int a, int n);

int main()

{

 int a=2, n=30;           // int limit == 4294967295;
                          // Power(2,30)==1073741824
                          // Power(2,31)==2147483648
                          // Power(2,32)==4294967296 out of limit =>
Power(2,32)==0

 cout << "Power(" << a << "," << n << ")= " << Power(a,n) << endl;
 cout << "Power(" << a << "," << n+1 << ")= " << Power(a,n+1) << endl;

 system("PAUSE");
 return 0;
}



uint Power(int a, int n)

{
 int i=1;
 uint r=1;

 for (i=1;i<=n;i++)
 {
 r=r*a;
 }
 return r;
}
-------------------------------End Code---------
Hope this helps.

--------------------------
http://mudeth.tripod.com

----- Original Message -----
From: "Jose Gana" <jg...@ho...>
To: <dev...@li...>
Sent: Saturday, June 15, 2002 8:59 PM
Subject: [Dev-C++] weird result


> Hi!
> Sorry if it is too obvious!
>  I am new in C++. I got 2^30= Power(2,30)= - 2147483648 in stead of +
2147483648 in my program.
>
> I must have done something wrong. But I can figure it out. Can somebody
help me out?
> [program follows]