There are different kinds of port in a system unit. The ports are :
- Serial port
- Parallel port
- Universal Serial Bus (USB) port.
- FireWire port
- special purpose ports
- MIDI port
- SCSI port
- IrDA port
SERIAL PORT
A serial port is a socket on a computer used to connect a modem, data acquisition terminal or other serial devices via a slow-speed serial interface.
A serial port is used to connect a device to the system unit by transmitting data one bit at a time.
Earlier PCs used the serial port for the mouse, and earlier Macintosh models used the serial port to attach a printer.
Today, the serial port is a legacy interface, having been superseded by the USB bus. An example of a serial port is the COM (communication) port.
PARALLEL PORT
A parallel port is a socket on a computer used to connect a printer or other parallel devices via the computer's parallel interface.
Unlike a serial port, a parallel port is an interface that connects devices by transferring information more than one bit at a time. Originally, parallel ports were developed as an alternative to the slower speed serial ports. Many printers connect to the system unit using a parallel port.
This parallel port can transfer eight bits of data (one byte) simultaneously through eight separate lines in a single cable. An example of a parallel port is the printer port.
USB PORT
A USB port is a socket on a computer or peripheral devices into which a USB cable is plugged in. A USB port, short for universal serial bus port, can connect up to 127 different peripherals together with a single connector.
It's used to connect all kinds of external devices, such as external hard drives, printers, mouse and scanner. It can transfer data to a speed of 12 megabits per second.
USB ports began to appear on PCs in 1997, and Windows 98 was the first Windows to support it. Within a few years, the USB became popular for connecting nearly every external peripheral device. Now that it is replacing the serial and parallel ports on a PC, at least four USB ports are standard on every computer.
FIREWIRE PORT
Previously the FireWire port is called IEEE 1394 port, a personal computer (and digital audio/video) serial bus interface standard.
FireWire is similar to a USB port in that it can connect multiple types of devices that require faster data
transmission speeds. Usually camcorders and other video equipment use this port to transmit data on a computer. Data can move across the port at up to 400 megabits per second.
Apple invented this technology and had branded it as FireWire. It was also adopted as an industry standard and is called IEEE 1394 on non-Apple computers. Up to 63 devices can be daisy-chained to one FireWire port.
Daisy-Chain
A bus wiring scheme in which, for example, device A is wired to device B, device B is wired to device C, device C to device D etc.
SPECIAL PURPOSE PORTS
There are four special purpose ports, which are:
MIDI port
It is designed to connect the system unit to a musical instrument, such as an electronic keyboard.
SCSI port
It is a special high-speed parallel port used to attach peripheral devices such as disk drives and printers..
IrDA port
Some devices transmit data via infrared light waves. For these wireless devices to transmit signals to a computer, both the computer and the device must have an IrDA port.
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