This is actually more subtle than one would think. Say you were trying to talk to three UART registers at 0xA000, 0xA004, and 0xA008. It's legal to access:

This is actually more subtle than one would think. Say you were trying to talk to three UART registers at 0xA000, 0xA004, and 0xA008. It's legal to access: *(volatile uint32_t *)(0xA000); *(volatile uint32_t *)(0xA004); *(volatile uint32_t *)(0xA008); The struct equivalent of this would be something like: struct UART_Peripheral { volatile uint32_t control; volatile uint32_t txdata; volatile uint32_t rxdata; }; struct UART_Peripheral *uart0 = 0xA000; uart0->control; uart0->txdata; uart0->txdata; As long as your structure is packed/aligned correctly, this is perfectly valid C. You can enforce the structure packing with an __attribute__ ((__packed__)) if using GCC or Clang. I think MSVC has a pragma for it. I know that the C language spec allows for structure padding, but I'm not sure if the concept is applicable if every member of the structure is the native word-size of the target CPU. But regardless of whether the spec specifies this expicitly or not, I've never seen a compiler insert padding in-between struct members that are already word-aligned. So the code might be very slightly questionable if written in pure C with no packing pragmas/attributes - but even then it would probably work on almost every target. And if used with the right pragma/attribute for your compiler, it's a perfectly valid construct. And it's also a common one - especially in embedded work or hardware drivers.