Hi what is fifo means

What does FIFO mean?
FIFO = First In, First Out.

It's used in a queue. The first thing into the queue is the first thing out of a queue. It's like standing in line at a bank. The first one to enter the line is the first one to be waited on. It's the same as FCFS = First Come, First Served.

The other method used in queues is LIFO, Last In First Out. This is like a stack of dinner plates. The one on top is the "Last" one placed there (Last In). It'll be the first one used when a new plate is required. This is sometimes called FILO, First In, Last Out.

More information:

FIFO - computing (http://en.wikipedia.org/wiki/FIFO_%28computing%29)

LIFO - computing (http://en.wikipedia.org/wiki/LIFO_%28computing%29)

FIFO and LIFO accounting (http://en.wikipedia.org/wiki/FIFO_and_LIFO_accounting)