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cmultiplication

Multiplication of three numbers in c give a wrong results?

I can't belive what's happen in my program

double den = 180*3600*10000 ;

in debugging a got this value -2109934592.0000000

any help please ???

you can try this simple code

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

int main ( int argc , char *argv )
{
double denominator =  10000*180*3600 ;

printf("%f \n", denominator ) ;
return 0 ;
}
Solution

  • With the full code in the question we can now see it's an integer overflow.

    10000 * 180 * 3600 = 6,480,000,000.

    This is greater than 2,147,483,648 which is the max value of a 32-bit signed int. The results of the multiplication overflows to -2,109,934,592 and is then converted to double.

    To get the right result make one of the numbers a double before you do the multiplication:

    10000.0 * 180 * 3600