We know that all of the loyal Computer Tips readers are ever grateful for
this series of tips, and you have probably all been wondering what you can
do to thank us for all this information.
Your first tip today is...
|When buying someone a gift, buy them something that they already have a lot of, because that is obviously something that they like.|
Now, having said that, you would think that there would be some limit to how many "things" (which we computer people might call peripheral devices) we could actually connect to our computer. Historically, allocating the precious resources of your system unit to multiple peripheral devices has been a major problem. Probably the most onerous culprit in this endeavor has been trying to assign a unique IRQ (interrupt request line) to each device. The general rule has always been that each device had to have its own separate IRQ,
Good news is here! No longer do we have to crawl around on the floor plugging and unplugging devices. No longer do we have to remove the cover of our computers to install and remove devices (although, admittedly, this is fun to do). No longer do we have to fight the IRQ battle.
Universal Serial Bus (USB) is a relatively new external input/output interface that greatly enhances the portability of peripheral devices. USB devices are external to your actual system unit, so they are much more accessible than internal devices -- you need not remove the cover of your computer to install or remove a USB device.
USB devices are Plug and Play, so setup and configuration is relatively easy. USB devices are even hot swappable, meaning that you shouldn't have to reboot your computer just because you have plugged in a new USB device.
USB supports up to 127 devices (yes, up to 127 devices!), arranged in a tiered star topology (see the diagram to the right). Most new computers today come supplied with two USB ports. Additionally, many USB devices are equipped with one or more USB ports into which you can plug yet another USB device, daisy-chaining your USB devices one after another. In the diagram to the right, a USB-enabled keyboard (on the far right of the diagram) plugs into the host computer; the keyboard is equipped with a USB port, into which a digital camera can be plugged. Plugging your camera into your keyboard is certainly much more convenient than getting down onto the floor and crawling under your desk to find a port on the back of your computer! Thus, one of the nice features of USB is the ease with which you can connect devices physically. That is, your ports can be made to be easily accessible.
You can purchase inexpensive multi-port USB hub devices which will support several USB devices. In the diagram, a 3-port hub is used (in Tier 1). A USB scanner, a USB CD-RW drive, and another hub are plugged into the 3-port hub.
One of the biggest advantages of USB is that the entire chain of devices requires only a single IRQ from the host computer. With modern PCs suffering from an interrupt shortage, this is a major benefit, one which should spur the adoption of this interface for lower-speed devices.
The availability of USB devices has grown through the past year to the point that USB should probably be a consideration for just about any peripheral device that you buy.
The figure to the right shows the contents of My Computer for a computer
which has a USB camera and a USB memory card reader installed.
Note that the memory card reader simply shows up as the E: drive.
You can open files from that E: drive just as you would any other drive.
Thus, take your pictures with the digital camera, pop the memory card out,
put the memory card in the reader, and your image files are immediately accessible.
(In the computer shown here, you can alternatively hook the camera directly to
a USB port with a cable and read image files from the camera rather than taking
the memory card out of the camera; either way, reading the files is extremely easy,
just like working with any other drive.)