Power
The power cord connects the computer to electrical power. It is a thick, round cable with a three-prong plug on one end and a three-hole plug on the other.
 If you are ever working on the inside of the case, be SURE that this cord is disconnected, else you might find out what it feels like to stick your finger in an electrical socket. Zap!
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Fan
The fan that you can see on the back of the computer is not a connection, but it is critical to the health of your computer.
It cools the power supply.
There is at least one other fan inside the computer, which keeps air flowing inside the case to remove the heat that all this processing generates. If things get too hot inside the casing, the CPU will fail to calculate accurately. You will get wrong answers, the wrong commands will be executed, there may be unpredictable crashes of your programs. This could be annoying or disastrous, depending on exactly what happens. If you have trouble only after the computer has been on for awhile, you can put HEAT on the top of your list of suspects.
Never block
the vent holes in your computer's case. Blow the dust off the blades from time to time.
Noise: When your computer first starts up, most of the noise you hear
comes from the fans.
If you ever fail to hear
a fan running, don't operate the computer until it is fixed or you'll be risking serious damage from heat.
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Keyboard
   The keyboard plugs into
the computer with a round connector, which can only fit one way. Recent
keyboards use a PS/2 connector, which is smaller than the old style keyboard connector.
The standard color coding scheme uses purple for the keyboard connector and
port, to make it easy to find the right port
for each connector. Not all manufacturers use the standard scheme.
  The barrel of the connector usually has a mark or channel
or a flat area to show where the "top" of the plug is. That spot should match the "top" of the computer-side
port. In tower cases the "top" is not toward the top of the case when it is in use, but toward the "top" as it is laying open for being worked on.
Connecting or
disconnecting a device with a PS/2 connector can cause a power surge to your
motherboard, which can ruin it. The damage will not be visible, but it will
definitely not be repairable.
Some cases make it a little hard to get the keyboard plugged in firmly. When computer boots, it checks for the presence of a keyboard and will not continue if it can't find one. If this happens while your keyboard is plugged in, first shut down the computer and unplug the keyboard, then plug it up again. Try to be sure that the plug is fully seated. Then reboot.
Keyboards can fail, especially after a session with spilled liquids or crumbs. So keep such away from your computer working area. Your keyboard may recover from a swimming session after it dries out if the liquid did not leave anything behind like sugar or tea leaves.
Heavy use will eventually wear out the electrical contacts in the keyboard, as in any electrical device.
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PS/2 Mouse
 
Newer mice use a PS/2 connection instead of a serial connection. The port and
the connector are light green, if the manufacturer has followed the standard
color scheme.
Connecting or disconnecting a device with a PS/2 connector
can cause a power surge to your motherboard, which can ruin it. The damage will not be visible, but it will definitely
not be repairable. (I didn't get this warning myself until AFTER I discovered it by expensive, accidental
experiment!)
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USB
 The Universal Serial Bus will soon be used for nearly all peripherals instead of the variety you see in the diagram. The computer chip on the main board can automatically recognize any USB device and assign the resources and power that it needs. This avoids the hair-pulling sessions that commonly go with the installation of a new device.
A USB device can be connected or disconnected at any time without having to shut down or reboot the computer.
A USB device can send data at 12 Mbps for devices like scanners and printers or at 1.5 Mbps for keyboards and joysticks.
If you connect a hub to the USB port on the back of the computer, you can then connect up to 127 other USB devices to the hub. They will have to share power and resources, of course, but many can work at the same time. No more problems with running out of connectors!
Most USB cables are 5 meters long (16.5 feet). This length allows for
the signal to get through properly. If you need a longer cable, you can hook up
several 5 m. cables and some USB hubs in a chain - up to 25 meters.
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Parallel Port  
A parallel port is used primarily by printers. Scanners and external storage devices of many types also connect to the parallel port. USB connections are replacing the parallel port.
A serial port sends data one bit at a time while parallel ports can send 8 bits at a time. The parallel port uses a 25 pin female connector.
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Modem 
An internal modem has connectors for phone lines, both "in" and "out". The "in" line runs from the telephone wall outlet. The "out" line runs from the computer to another device, usually either a FAX machine or a regular telephone.
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~~ 1 Cor. 10:31 ...whatever you do, do it all for the
glory of God. ~~
Last updated:
22 Jan 2008
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Digital monitors have a different connector
without pins and require a digital video
card.
A
network patch cable is round but the connector is similar to a telephone
connector but wider.
