PS/2 Ports

• The PS/2 standard, introduced by IBM in 1987
  
• stands for Personal System/2.
  
• A PS/2 port is an electronic receptacle or plug found on computers.
  
• It accepts a PS/2 cable with a mini-DIN connector
  
• Most often used to plug in a keyboard or mouse.
  
• The PS/2 port is female while the mini-DIN cable is male. The connector is small with a diameter of about 1/3 inch (9.5mm).

Serial ports

• Serial ports are also known as communication or COM ports.
  
• The COM ports have been used to connect devices which have a two way communication with the PC.
  
• The newer parallel port standard now allows the parallel port to perform high speed communication with the PC.
  
• A typical system includes one or two serial ports.
  
• The serial port can be used to connect devices such as modems, plotters, printers into a PC.
  
• The recommended cable length is 50 feet.

Parallel ports

• Parallel ports were originally designed to connect printers. Parallel ports are general purpose ports.
  
• It is faster than the serial port.
  
• They also can send and receive data.
  
• A parallel port contains eight lines so that it can send 8 bits at the same time on those eight lines, which makes it faster than serial ports.
  
• One problem of parallel port is that; you cannot extend the length of the cable of a parallel port to a greater extended due to the errors occurring if you do so.

USB port (Universal Serial Bus)                     
USB is a standard used in PC to connect devices in a Plug and Play manner. Plug and Play means, that you just connect the device to the computer and you can straightway use it without the need of installing and configuring or rebooting.
USB is an external bus standard designed to connect devices externally to a PC.
USB standard is becoming very popular because of its less over head due to Plug and Play.

RJ 45

• Short for Registered Jack-45
  
• an eight-wire connector used commonly to connect computers onto a local-area networks (LAN), especially Ethernets.
  
• RJ-45 connectors look similar to the ubiquitous RJ-11 connectors used for connecting telephone equipment, but they are somewhat wider.