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I'm having trouble understanding the output of this program int main() { double x = 1.8939201459282359e-308; double y = 4.9406564584124654e-324; printf("%23.16e\n", 1.6*y); printf("%23.16e\n", 1.7*y); printf("%23.16e\n", 1.8*y); printf("%23.16e\n", 1.9*y); printf("%23.16e\n", 2.0*y); printf("%23.16e\n", x + 1.6*y); printf("%23.16e\n", x + 1.7*y); printf("%23.16e\n", x + 1.8*y); printf("%23.16e\n", x + 1.9*y); printf("%23.16e\n", x + 2.0*y); } The output is 9.8813129168249309e-324 9.8813129168249309e-324 9.8813129168249309e-324 9.8813129168249309e-324 9.8813129168249309e-324 1.8939201459282364e-308 1.8939201459282364e-308 1.8939201459282369e-308 1.8939201459282369e-308 1.8939201459282369e-308 I'm using IEEE arithmetic. The variable y holds the smallest possible IEEE number. The first five prints show a number which is twice y as I would expect. What is confusing me is that the next five prints show different numbers. If 1.6*y is the same as 2.0*y then how can x + 1.6*y be different from x + 2.0*y ?

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