The various connectors and ports on thecomputer allow it to communicate with the many different devices andperipherals attached. Because there are so many cables and cords attached tothe back of the computer, and so many different types of connectors, it oftenseems a little intimidating to the newer user. Although there are some deviceswhich may use the same connector or port, the individual devices and theircords can only physically attach to one certain type of connector; so don'tfeel nervous about hooking your system together.
There's really no way you can do any harmto your computer just by hooking it up, as long as you follow a few commonsense rules:
The first thing to know is the differencebetween a male and female connector. The male connector fits inside the femaleconnector. If the connector has pins protruding from it, its a male connector.If the connector has holes for the pins to fit into, then its a femaleconnector. When you hook something up to your computer, the male and femaleconnectors are hooked together. The connectors on the back of your computer arecalled input/output ports (i/o ports) or communication ports.
The second thing you should remember isthat when you join a connector to a port, they must have the same shape and thesame number of pins or holes. In other words, a square peg won't fit into around hole, and its not wise to try to jam fifteen pins into nine holes (partof the 'common sense' thing I was talking about).Which brings us to anothervery important point, never force anything.
Here's one that's hard to do. Always makesure the computer is off before attaching connectors or cables to any ofthe ports. This can cause little power gliches (another technical word) thatcould corrupt an open file or cause a program to freeze. It can even cause asmall short that could damage or ruin components inside your computer. I know,you've done it a hundred times and never had a problem. Well, that's good. Ifyou want to continue to practice risk management, that's your perogitive, butbe aware of the possibilities and don't be surprised when you finally getburned. USB ports are the only ports that should be consideredhot-swappable (this means they can be plugged in or unplugged while the machineis on).
Only one more thing to remember. There aresmall hexagonal nuts on either side of many of the ports on your computer.These allow you to screw the connectors in so they don't accidentally fall outor loosen. They just have to be screwed down, they do not have to betightened. These nuts are actually the heads of small bolts that passthrough the back plate on your computer and are attached with a small nut onthe other side. If you tighten the screws too much, then when they're undone,they may take the bolt with them and the small nut may fall off inside thecomputer (onto the motherboard or an expansion card). Not a good thing.
Now that we know the basic rules, let'stake a look at some of the connectors or ports you might find on your computer.
DB Connector
The most common connector is the DB connector. It's sort of a 'D' shapeand is sometimes called a D-shell connector (go figure). It's designated asDB-x, with 'x' being the number of pins or holes on the individual connector.So a DB-9 female connector would be a 'D' shaped connector with 9 holes. Thiswould receive a cord with a DB-9 male connector (with 9 pins).
If you find a DB male connector port on theback of your computer, (either a DB-9 male or a DB-25 male) it'sgoing to be a serial port. Serial ports are also called COM ports or RS-232ports (Reference Standard #232 as referenced by IEEE*). Serial ports transmitdata one bit at a time and are relatively slow compared to other ports.However, they are plenty fast enough for some external devices such as a mouse,or an external modem. Because only one bit at a time is passed along a serialcable, it can travel a fair distance before data integrity is challenged (orerrors start to occur). A serial cable shouldn't be more than 50 feet inlength.
Incidentally, in case you were wondering,if you have a device with only nine holes on its connector, and only a DB-25male serial port to connect to, all you need is a 9 to 25 pin adapter. There'sno difference between a 25-pin serial port and a 9-pin serial port other thanthe fact that the DB-25 male has sixteen extra pins that it doesn't use.
If you have an older computer, and see a DB-9female connector on the back, it's probably a video connector for an olderEGA or CGA monitor. My guess is that you won't see one on your computer.However, if the question should ever come up, it could also be a Token Ringnetwork adapter port.
Look on the back of your computer, you maybe able to find two different DB-15 female connectors. If you see threerows of five holes, then it's your VGA or SVGA video monitor adapter. If yousee only two rows (one of eight holes and one of seven), then it's probably ajoystick adapter.
A DB-25 female connector on the backof your computer is going to be a parallel port. Parallel ports can transmitdata eight bits at a time which creates a noticeable speed increase over serialports. Most commonly used as printer connections, several other devices now usethe parallel port such as tape backup systems, Zip drives and scanners to namea few. These devices are generally fitted with what is referred to as apass-through port. This means that you can hook up your scanner to the parallelport (DB-25 female) and then connect your printer to the DB-25 connector on theback of the scanner and have access to both devices. This usually works wellbut does pose some problems. First off, the device has to be turned on for thepass-through port to work. To take this one step further, the device often hasto be turned on before the computer is booted, to be recognized properly andfor the right drivers to be loaded at startup. Also, users tend to think thatthey can daisy-chain these devices. In other words, connect their scanner tothe computer, attach their Zip drive to the back of the scanner, their tapedrive to the back of the Zip drive, and then their printer to the pass-throughport on the back of the tape drive. Believe it or not, I've seen this done andI've seen it work (more or less). I've also seen it work one day and not thenext. It's a hit and miss sort of thing (more miss than hit) and I wouldn'ttrust the integrity of the data past the second device.
Another thing to keep in mind, is that thecable on a parallel device shouldn't be more than 10 feet long. Data errors canoccur beyond this distance.
DIN Connector
TheDIN connector is a small round connector, usually with a keyed slot for properorientation. Again, it's designated as DIN-x, with 'x' representing the numberof holes or pins on the connector. It comes in a couple of different sizes andit's been used on computers about as long as the DB connector has. It's afairly popular connector because of its small size and solid connection.
The most common DIN connector would have tobe the DIN-5 keyboard connector. Its the largest of the DIN connectorsthat you're going to find on your computer and its been around for a long time.If you own a newer computer, then the DIN-5 has probably been replaced with aDIN-6 (mini-DIN or PS/2) connector.
The PS/2, or DIN-6 connector,was mainly used by Macintosh computers for the longest time (Macintosh alsoused a DIN-8 connector for their printer). You may hear them referred to as a miniDIN-6 connector. They're smaller and more compact than the typical DIN-5connector and have become the standard for both the keyboard and the mouse onnewer PCs. If this is the case on your computer, then the two DIN-6 femaleports on the back of your computer are going to look an awful lot alike, andyou need to distinguish between the mouse port and the keyboard port beforehooking them up. They may be color coded or they may have a little icon besidethem representing their use. Whatever the case, you're not going to do any harmif you accidentally get these two devices switched. Your mouse won't work, oryou'll get a keyboard error at boot up. Your first course of action for troubleshootingthis type of problem should be to check the connection anyway.
Another port you could find on the back ofan older computer is the DIN-9. It would be another mini DIN port with 9sockets. A bus mouse or a hand-held scanner may use this type of port, but it'sunlikely that you're going to find one on a newer computer.
RJ Connectors
TheRJ connector is used for communication devices. If you live in North Americaand have a jack on your wall that your phone connects to, that's an RJ-11connector. Now, the RJ-11 connector or port doesn't have 11 pins or 11 holes.As a matter of fact, it only connects 4 or 6 wires.
You may have an RJ-11 connector on the backof your computer if you have an internal modem. This is to hook a phone line upallowing communication with other computers and access to the Internet and theWorld Wide Web.
If you see two RJ-11 connectors side byside, it means that you can hook the phone line to your computer using the onejack, and then an extension phone can be plugged into the other jack. A lot ofmodems today allow for fax and voice capabilities. This means that you can faxfrom your computer, it can double as an answering machine that records messagesand voice mail, and, if you have speakers and a microphone, you can even use itas a speakerphone.
An RJ-45 connector looks much likethe RJ-11, only larger. It connects 8 wires and is used for network ethernetconnections. If you see and RJ-45 connector or port on the back of yourcomputer then there's two possibilities; Your computer is hooked up to anetwork or intranet, or, you have cable hookup to the Internet and the WorldWide Web. The latter uses an RJ-45 connection between the cable modem and thenetwork interface adapter (which is the same adapter you would be using for anetwork connection).
As you can see, the RJ connector isdesignated as RJ-x. But the 'x' doesn't tell you the number of connectors thatthe port has like other ports. At one time, I thought it might designate thesize of the jack. The RJ-45 is larger than the RJ-11, but the RJ-12 is smaller(this is the connector between your phone and the handset), so I guess thatdoesn't hold water either. At this point, I become disinterested... If you knowthe answer, let me know and I might change this paragraph. But mainly what youneed to know is, the RJ-11 connects 4 or 6 wires, is used on modems andtelephones, and is smaller than the RJ-45 which is used for ethernetconnections to network interface cards.
Centronics Connectors
TheCentronics connector is a parallel interface connector. It has eight paralleldata lines which allow data to travel eight bits at a time. (remember theparallel DB-25 female port). The Centronics connector is designated asCentronics-x, with 'x' representing the number of teeth or connections it has.It kind of looks like an elongated DB connector with metal teeth as connectorsinstead of pins. Some connectors have small clips on either side to hold it inplace.
You're probably not going to find thisconnector on the back of your computer, but on the opposite end of yourparallel cable where it connects to the printer. This will more than likely bea Centronics-36 connector.
If you have SCSI or know what SCSI is, thenyou should know that SCSI can use a Centronics-50 or Centronics-68 connector,as well as a DB-25.
USB(Universal Serial Bus)
UniversalSerial Bus is a relatively new connector that was meant to replace Serial andParallel ports. Its a flat, keyed connector with four contacts that wasdesigned for mid-speed peripherals such as scanners, keyboards, mice,joysticks, printers, modems and some CD-ROMs. USB is unique in that itis completely hot-swappable. In otherwords, you can plug it in or unplug itwhile the computer is on. Your computer should recognize it as soon as its pluggedin, and you should have use of the device immediately.
USB allows you to daisy-chain up to 127devices. This means that you could have a joystick plugged in, with a printerplugged into that, and a scanner plugged into the printer, etc...
USB was first introduced with new computersaround 1997 and the final version of Win95 (SR2) provided very limited supportfor it. A few problems seemed to develop at first. You had to have a Pentiummachine with a BIOS that supported USB, and it had to be enabled in the setup.Your computer had to have USB ports on it, or pins that allowed for theattachment of a USB interface. Aside from that, you could install a USB adaptercard in one of your PCI slots. Then, there weren't a lot of USB devicesout there.
I think one of the biggest problems thatarose at first was that people weren't using the proper Operating System. Theearly versions of Win95 did not support USB. Also, a lot of machines shippedwith USB ports or capabilities before the BIOS supported it completely.Updating, or flashing the BIOS could sometimes solve the problem.
Despite the growing pains, Windows 98, andcomputers shipped after 1998 provide excellent support for USB; and the numberof devices have increased dramatically.
I have a USB mouse and scanner that I canhot swap between my desktops and my laptop with immediate access. To tell thetruth, I haven't even tried daisy-chaining together, and as I write this, I'mthinking about going out and buying a keyboard just so I can try it. I thinkUSB is fantastic, and I'm looking forward to the day when all peripherals arethat easy to install and configure.