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In computer networking, a port or port number is a number assigned to uniquely identify a connection endpoint and to direct data to a specific service. At the software level, within an operating system , a port is a logical construct that identifies a specific process or a type of network service .
This is a list of TCP and UDP port numbers used by protocols for operation of network applications. The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) only need one port for bidirectional traffic. TCP usually uses port numbers that match the services of the corresponding UDP implementations, if they exist, and vice versa.
In contrast to the frequency domain analysis of the classical control theory, modern control theory utilizes the time-domain state space representation, [citation needed] a mathematical model of a physical system as a set of input, output and state variables related by first-order differential equations. To abstract from the number of inputs ...
The mutual goal of IEEE Std 91-1984 and IEC 617-12 was to provide a uniform method of describing the complex logic functions of digital circuits with schematic symbols. These functions were more complex than simple AND and OR gates. They could be medium-scale circuits such as a 4-bit counter to a large-scale circuit such as a microprocessor.
A male D-subminiature DE-9 connector on an IBM PC compatible computer (with serial port symbol) used for an RS-232 serial port A female D-subminiature DE-9 connector on an RS-232 cable. A serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. [1]
The open systems theory is the foundation of black box theory. Both have focus on input and output flows, representing exchanges with the surroundings. In systems theory, the black box is an abstraction representing a class of concrete open system which can be viewed solely in terms of its stimuli inputs and output reactions:
In computer science, the process calculi (or process algebras) are a diverse family of related approaches for formally modelling concurrent systems.Process calculi provide a tool for the high-level description of interactions, communications, and synchronizations between a collection of independent agents or processes.
A modern control room where plant information and controls are displayed on computer graphics screens. The operators are seated as they can view and control any part of the process from their screens, whilst retaining a plant overview. Process control of large industrial plants has evolved through many stages.