. Does it matter how I turn off electronic devices? I have installed a power surge strip and it's easiest for me to simply turn off that strip. Is it better for the devices to turn them off individually first? For the computer itself, I perform the shutdown procedure first. — A, Seattle, Washington
As long you shutdown the computer first, turning off the power strip is fine. Essentially all modern household computer devices are designed to shut themselves down gracefully when they lose electrical power and that's exactly what they down when you turn off the power strip.
In fact, turning off the power strip is likely to save energy as well. Many computer devices have two different "off" switches: one that stops them from doing their normal functions and one that actually cuts off all electrical power. Computers in particular don't really turn off until you reach around back and flip the real power switch on the computer's power supply. The same is true of television monitors and home theater equipment.
In general, any device that has a remote control or that can wake itself up to respond to a pretty button or to some other piece of equipment is never truly off until you shut off its electrical power. Our homes are now filled with electronic gadgets that are always on, waiting for instructions. Keeping them powered up even at a low level consumes a small amount of electrical power and it adds up. Last I heard, this always-on behavior of our gadgets consumes something on the order of 1% of our electrical power. Whatever it is, it's too much. So by turning off your power strip and completely stopping the flow of power to your computer, your speakers, your monitor, etc., you are saving energy. You lose the convenience of being able to turn everything on from your couch with a remote, but who cares. Energy is too precious to waste for such nonessential conveniences.
. What kinds of things get stored in read-only memory, as opposed to storing them on the hard drive?
When you first turn on a typical computer, it must run an initial program that sets up the operating system. This initial program has to run even before the computer is able to interact with its hard drive, so the program must be available at the very instant the computer's power becomes available. Read-only memory is used for this initial bootup operation. Unlike normal random access memory, which is usually "volatile" and loses its stored information when power is removed, read-only memory retains its information without power. When you turn on the computer, this read-only memory provides the instructions the computer uses to begin loading the operating system from the hard drive.
. How does an integrated circuit perform computations? I know that it has transistors embedded into it, but how can a circuit of semiconductors be used for multiplication? — DF, Marina Del Rey, California
The transistors used in digital integrated circuits, including microprocessors, act primarily as electronically controlled switches. These transistor switches permit the electric charge on or electric current in one wire to control the electric charge on or current in another wire. In digital electronics, a wire's charge or current state is used to represent a single binary digit—either a 1 or a 0. By combining transistors in modestly complicated arrangements, the states of several wires together can control the states of several other wires. This increased complexity allows for simple functions such as binary addition to be performed—for example, the charges on two wires can be used to control the charges on two other wires so that the charges on the second pair of wires represent the single binary sum of the two individual numbers represented by charges on the first pair of wires. More complicated adders can be assembled from more transistors and finally multipliers can be assembled from a collection of adders. Overall, it only takes a few arrangements of electrically controlled switches to form the primitive elements from which incredibly complicated digital processors can be built.
. If an 8-ohm speaker was connected in parallel to an 8-ohm resistor, would the new impedance be 4 ohms?
Yes. When you connect two 8-ohm devices in parallel, so that they share a current between them, they act as a single 4-ohm device.
. How does a computer chip work? — JM, Austin, TX
A computer chip is also known as a digital integrated circuit. It is typically a thin wafer of silicon, cut from a single crystal of that element. The surface of the wafer has been chemically modified and it has had intricate patterns of aluminum wires and other structures cut and deposited photographically on its surface to form enormous numbers of transistors and other special structures. Each of these transistors is an electronically controllable switch. A tiny adjustment in the electric charge on the control element of one of these transistors—its gate—can dramatically alter that transistor's current carrying ability. These transistors work together to perform task that range from remembering one bit of information to multiplying two huge numbers together. The millions of transistors on a typical computer chip are able to perform extremely complicated tasks, as we see everyday in modern computers.
. How does an integrated circuit store so much information?
An integrated circuit is formed by using photographic techniques to sculpt the surface of a silicon crystal, to add chemicals to the silicon, and to deposit layers of other materials on top of the silicon. As part of this sculpting and coating process, a typical computer chip will have tiny memory cells formed on it. These cells usually consist of a tiny pad of aluminum on which a small amount of electric charge can be stored. To store one piece of information, a "bit", on one of these pads, electronic devices called MOSFETs—built right into the silicon surface—are used to control the flow of charge onto the pad. The amount of charge on the pad determines the bit's value. The charge remains on the pad, thus storing the bit, until it's time to recall the bit. At that time, the MOSFETs allow the charge to flow off the pad and into electronic devices that determine what the stored value is.
. Is it possible to have memory in a computer monitor?
Yes. In fact, many modern monitors do have memory in them. However, this memory isn't used for the same information that's handled in the computer itself. Instead, the monitor's memory is used to control the monitor's behavior. Many sophisticated monitors are equipped with digital controllers that are almost full-fledged computers themselves. These controllers can adjust the size and position of the screen image and the manner in which that image is built. This work by the controller allows the monitor to respond properly when the computer changes the screen resolution or the refresh rate (the frequency with which the image you see is rebuilt). The controller requires memory to operate and it also needs to store data that it can expect to recover next time you turn the monitor on. On a sophisticated monitor, you adjust the image size by pushing buttons under the screen and the monitor uses special memory to record your button presses. When the monitor is turned on, it recalls its record of your adjustments and uses them to return the image size to what it was last time the monitor was on.
. How do notebook computer monitors work?
These displays use liquid crystals, liquids that contain long chain or disk-shaped molecules. These molecules can be aligned by external electric fields or by their own interactions with one another to form very orderly arrays; hence the name "liquid crystals". The extent to which these molecules are oriented determines their optical properties. A notebook computer uses electric fields to orient or disorient the liquid crystals and control their optical properties. With some help from other optical devices, the notebook computer can make these liquid crystals block or unblock light to appear dark or light. Adding color filters allows them to produce colored images on their screens.