Struct members order does make a difference

Memory usage: decreased

General modern computer address their memory in word-sized chunks, which mostly is 4-bytes word for x86 architecture or 8-bytes word for x86-64 architecture. To maintain the higher performance, computer applies rules of data alignment, which in practice means that some useless bytes can be added between variables so that the variables are accessible at addresses equal to multiple of the word size. The knowledge of that can be essential when designing structures for systems with strict memory requirements since it will allow you to reduce the size of struct.