First In First Out (FIFO) is an overflow principle in memory technology and shift registers. With this technique, when the memory capacity is fully utilized, the first data unit entered or the first backup read in is also the first to be read out or deleted again.
With this method, also known as First Come First Served( FCFS), all frames are stored in a single queue, in the order in which they arrived. Readout is done sequentially according to the order they arrived. FIFO has a small delay time.