overflow.c

#include <stdio.h>
#include <limits.h>

int main()
{
	printf("an int has %lu bytes ", sizeof(int));
	printf("and it can fit up to %d inside it\n", INT_MAX);
	printf("a long long has %lu bytes ", sizeof(long long));
	printf("and it can fit up to %lld inside it\n\n", LLONG_MAX);

	printf("20000000000 is a number that needs 64 bits\n");
	int factor1 = 20000000, factor2 = 1000;
	printf("however, these factors fit inside 32-bit ints: %d and %d\n", factor1, factor2);
	printf("let's check if the multiplication works as ints: %d * %d = %d\n", factor1, factor2, 20000000 * 1000);
	printf("at least the compiler warned me about it!\n");
	printf("let's use long longs: %d * %d = %lld\n", factor1, factor2, 20000000LL * 1000);
	printf("what if we make only the *result* long long? (long long)(%d * %d) = %lld\n", factor1, factor2, (long long)(20000000 * 1000));

	return 0;
}