The SN74HC595N is an 8-bit serial-in, parallel-out shift register IC with additional features such as an 8-bit storage register, output enable control, and cascading capability. It is commonly used in digital systems to expand the output capability of microcontrollers or for driving LEDs and other display elements. With just three digital inputs, 8 digital outputs are created. Initially, these sound a lot like a basic 3 – 8 decoder but a shift register is a lot more flexible. While a 3 – 8 decoder can only set one of the 8 pins at a time, this shift register can dynamically switch all 8 pins between high and low in any combination.