#Queue fifo full
#Queue fifo code

#Queue fifo full

A FIFO is full when the write address register reaches the read address register. A FIFO is empty when the read address register reaches the write address register. It is often implemented as a circular queue, and thus has two pointers:Įxamples of FIFO status flags include: full, empty, almost full, and almost empty. Conversely, one may use either a leaky bucket approach or pointer arithmetic to generate flags in synchronous FIFO implementations.Ī hardware FIFO is used for synchronization purposes. One further note concerning flag generation is that one must necessarily use pointer arithmetic to generate flags for asynchronous FIFO implementations.

#Queue fifo code

A common implementation of an asynchronous FIFO uses a Gray code (or any unit distance code) for the read and write pointers to ensure reliable flag generation. An asynchronous FIFO uses different clocks for reading and writing and they can introduce metastability issues. Alfke was later a director at Xilinx.Ī synchronous FIFO is a FIFO where the same clock is used for both reading and writing. The first known FIFO implemented in electronics was by Peter Alfke in 1969 at Fairchild Semiconductor.

For FIFOs of non-trivial size, a dual-port SRAM is usually used, where one port is dedicated to writing and the other to reading. Storage may be static random access memory (SRAM), flip-flops, latches or any other suitable form of storage. In its hardware form, a FIFO primarily consists of a set of read and write pointers, storage and control logic. Electronics įIFOs are commonly used in electronic circuits for buffering and flow control between hardware and software. Some devices feature multiple FIFOs for simultaneously and independently queuing different types of information. Typically at least one FIFO structure is used per network connection. Ĭommunication network bridges, switches and routers used in computer networks use FIFOs to hold data packets in route to their next destination. In computing environments that support the pipes-and-filters model for interprocess communication, a FIFO is another name for a named pipe.ĭisk controllers can use the FIFO as a disk scheduling algorithm to determine the order in which to service disk I/O requests, where it is also known by the same FCFS initialism as for CPU scheduling mentioned before. #include #include using namespace std template class FIFO Queueing theory encompasses these methods for processing data structures, as well as interactions between strict-FIFO queues. A priority queue is neither FIFO or LIFO but may adopt similar behaviour temporarily or by default. FIFO's opposite is LIFO, last-in-first-out, where the youngest entry or 'top of the stack' is processed first. in the same sequence in which they arrive at the queue's tail.įCFS is also the jargon term for the FIFO operating system scheduling algorithm, which gives every process central processing unit (CPU) time in the order in which it is demanded. Such processing is analogous to servicing people in a queue area on a first-come, first-served (FCFS) basis, i.e. In computing and in systems theory, FIFO is an acronym for first in, first out (the first in is the first out), a method for organizing the manipulation of a data structure (often, specifically a data buffer) where the oldest (first) entry, or 'head' of the queue, is processed first.