Knowledge is knowing that sizeof(int) is implementation-defined. Wisdom is understanding how likely your code is to ever run on any platform where sizeof(int)

Knowledge is knowing that sizeof(int) is implementation-defined. Wisdom is understanding how likely your code is to ever run on any platform where sizeof(int) is not 4, and if the answer is "not really," then stop worrying about it. To succeed as a C programmer, you need both knowledge and wisdom.