simple question

[nieds]

I am a beginning programmer and this has been bugging me for a long time today, I can not see where I made an error, this program is suppose to return the prodoct of all even numbers from 2-100, but it only returns 0, I am just kind of brain dead that I can not find where I messed up, I know it is just simple mistake somewhere.

#include <stdio.h>

int main(void)
{
    int x, product;

    product = 1;
    for ( x = 2; x <= 100; x += 2)
        product = x * product;

    printf("the product is %d\n", product);

    return 0;
}

any help would be very appreciated

[cwr]

Change your code to show what is happening, you should see the error:

#include <stdio.h>

int main(void)
{
    int x, product;

    product = 1;
    for ( x = 2; x <= 100; x += 2)
    {
        product = x * product;
        printf("product is now %d\n", product);
    }

    printf("the product is %d\n", product);

    return 0;
}

[Dave_Sinkula]

Perhaps it overflows the range of integer values long before 100 is reached?

[edit]D'oh! Pokey.

[Maragato]

Perhaps it overflows the range of integer values long before 100 is reached?

[edit]D'oh! Pokey.

yes this is exactly the problem, Ive tested with smaller values and it works here.

[cwr]

Yeah, if you remember your times tables, everyone knows that the product of even numbers between 2 and 100 is 34243224702511976248246432895208185975118675053719 198827915654463488000000000000, far too big to be accurately stored in any native C type. Even the long double type results in accuracy loss when x reaches 52 on my implementation.

[dwks]

What's the maximum number that a long long can hold?

[Dave_Sinkula]

What's the maximum number that a long long can hold?

LLONG_MAX, which must be at least +9223372036854775807.

[Salem]

> What's the maximum number that a long long can hold?
See limits.h

[dwks]

I didn't have a compiler on that computer, but thanks for the suggestion.