Ports

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Ports - These are connectors found at the back of the computer which send and received data to and from the peripherals such as modems, monitors, printers, plotters and keyboards. Ports can be found directly on the motherboard but most are added with the use of separate expansion cards.

Serial Ports (COM Ports)

These are 25-pin male connectors which are used to connect the computer to a mouse, external modem, serial printer, plotter, graphic tablet or even another computer. There are two types, 9-pin and 25-pin. The 9-pin is more frequently used on 286 and 386 computers. The serial port itself is also referred to as an RS232 is a standard for serial communications, used in virtually all microcomputers. Serial ports are called serial because they send and receive information serially or in other words, one bit at a time. These ports are also referred to as COM ports. Most computers typically have two COM ports. Each COM port is defined as either COM 1 or COM 2. COM 3 and COM 4 are also available. A serial port allows a computer to send data over long distances by converting parallel data to serial data. Typical computers will have one or two serial ports, usually designated as COM1 and COM2. The "standard" port is a 9-pin male connector on the computer.

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The following table describes the pin connection for the 9-pin and 25-pin serial cable connectors.

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Parallel Port (Printer Port)

. Parallel ports are 25-pin female connectors. It is an 8-bit parallel connection with handshaking signals between the printer and the computer—these tell the computer when to start or stop sending data. A standard printer cable is configured with a 36-pin Centronics connector on the printer end and a standard 25-pin "D" (male) on the computer end. A standard 25-pin "D" (female) connector found on the back of the computer designates it as a parallel port This ports are designated as LPT ports. LPT is an abbreviation for line printer a device commonly used with this port. Just as COM ports have a number so do parallel ports.

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Parallel Pin Assignments

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. Just like modem cables, it is important for printer cables to have the correct pin connections. The following table describes the standard parallel pin assignments for the computer-end (25-pin) and the printer-end (Centronics) connectors.

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note : table to be added

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·Game Port This 15-pin female connector is used for joysticks and paddles. These are usually used to interface with game software.

·PS/2 Keyboard Port This 5-pin female connector connects the keyboard or a bar code reader to the computer.

·PS/2 Mouse Port This 5-pin female connector connects the keyboard or a bar code reader to the computer.

·USB Ports USB (Universal Serial Bus) is a serial bus standard to interface devices. It is popular with the highest speed, and security. USB supports Plug & Play system that allows easy installation; there are many devices, used with USB Port such as Mouse, Keyboard, Printer, Scanner, Modem, Camera Digital, etc. Mostly, the devices that interface with computer will be USB.