First In – First Out is the sequence in which certain tasks are processed or completed one after the other. In accounting, this is called a consumption sequence method, in computer science it is any method of storage in which those elements that were stored first are also taken out of the memory first.
In the field of merchandise management, FIFO is the usual procedure, because the oldest (first stored) inventories – seen from the perspective of the end of the period – should also be consumed or sold first if possible. FIFO thus also reduces the risk of storage. As a general rule, the items that are posted first in goods receipt are also entered in the goods issue first.
When it comes to the storage of bulk materials, the FIFO principle is only approximately fulfilled by a silo. Goods with a best-before date or expiry date are usually retrieved according to the FEFO procedure. For non-perishable bulk materials, on the other hand, the more cost-effective storage in stockpiles is used, which can only be removed from above, i.e. are considered according to the LIFO method. The difference between the two methods is particularly important for inventory valuation.
FIFO refers to a queue of computational unit from which the longest-waiting item is processed next. FIFO is a special way of storing and retrieving data. The queue in computer science is based on the FIFO principle. Items are retrieved in the exact order in which they were previously stored. At the operating system level, data connections organized according to the FIFO principle are called pipes.
A practical area in computer science where a FIFO is used is controllers, especially the serial port (RS232 port) on personal computers. The buffered chip uses a FIFO process to ensure that the first byte arriving at the serial port is the first to be processed by software in the computer. Byte protocols (e.g. by a mouse) thus remain linearly equivalent for “readers” (drivers) and “writers” (mouse). The same applies to the keyboard buffer.