"It would appear that we have reached the limits of what it is possible to achieve with computer technology, although one should be careful with such statements, as they tend to sound pretty silly in five years." -John von Neumann (1903-1957)
Electronics is the study of the flow of electrons. Beginning with the telegraph, people have used electrons for communication. With the development of electronic components, industries rapidly developed around radio, the telephone, and later television.
Beginning in the second half of the twentieth century, electronics began to play a major role in not only communicating information but also in processing it. As engineers developed ways to make electronic components smaller and smaller, the ability of computers to perform calculations grew at an unimaginable rate. The earliest computers filled large rooms with massive vacuum tubes. Today, a credit card-sized calculator, costing less than a dollar, has more computing power.
What happens inside a computer?
When you turn on your computer, you may hear the hard drive start to spin, an occasional beep, and the soft whirr of a fan. All of these sounds are incidental to the real operation of the computer, though. The "crunching" of data takes place at an incredible rate, but completely silently. What happens inside the computer as it works?
The main operating part of a personal computer is the microprocessor, or central processing unit (CPU), which functions entirely by performing mathematical operations. This processor is about the size of a box of matches but in fact it is the computer. Everything else around it is there to help the processor take in data and send out results.
Hardware is all of the physical components of a computer, including the CPU, hard drive, mouse, monitor, and keyboard. Software refers to the instructions that tell the computer what to do, including such things as the BIOS; operating system; and programs such as word processors, games, and e-mail programs.
When you turn on the power, it begins to "boot" (from "pulling itself up by its own bootstraps"). The first thing to come on is the Basic Input/Output System (BIOS), a small program permanently stored in the memory. The BIOS basically tells the computer that it is a computer and where to go to find out more. The BIOS tests all the hardware components and provides a set of instructions to the CPU about how to find and use them.
After the boot process is complete, the CPU takes over. The CPU is a huge collection of tiny electronic components. Top-of-the-line microprocessors, as I write this, have close to a billion components (most likely, more than a billion by the time you are reading it). Transistors act as switches controlling the flow of electrons, and capacitors can store or release electrons, creating on/off states that correspond to the zeros and ones of binary numbers. These are the basic units of information that the CPU processes by the billions every second.
The CPU has two functions: it manages the flow of data into and out of its millions of circuits and it carries out mathematical and logical (such as comparing two numbers) operations. Much of the flow management involves sending numbers to memory and then retrieving them when they are needed. Keeping numbers in memory when they are not actually involved in calculations frees the circuits of the CPU so they can work on more pressing calculations.
Everything that goes into the CPU, including words, pictures, and music, is coded numerically. The operating system is a program that translates all the signals coming from input devices—your keyboard, mouse, microphone, or the Internet, for example—into code that the CPU can process. It translates the output into an appropriate form for you to use—monitor, speakers, printer, and so on. Early computers used operating systems that were perhaps a few thousand lines of binary code to run simple tasks. Today’s operating systems occupy large sections of a hard drive with tens of millions of lines of code that instruct the computer to perform complex operations and to control sound, graphics, and other functions of the many programs we run on our computers.
In addition to the operating system, separate programs contain instructions for particular applications. For example, a video game program contains instructions for the CPU to perform a specific type of calculation in response to the motion of your mouse and then display the result as action on the monitor.
Although many people find that their computer runs slower after a year or two (or sometimes less), a computer does not wear out over time. The CPU and other components do not gradually become less efficient. They either work or do not work. It is possible that programs on your computer are demanding more resources than the computer has to work with. Unless you have up-to-date programs to scan for unwanted programs, the most likely cause of a slow computer is a virus or an accumulation of spy programs that use a Iot of your computing ability.
How are supercomputers different from regular computers?
There are some research projects that require massive amounts of computing. For example, models of the atmosphere and oceans are so complex that climate-change researchers must consider the tiniest variables. This type of detailed analysis is typically done on a supercomputer. How do supercomputers differ from the computer on your desk?
The speed of a computer can be measured as the number of floating point operations (FLOP or flop) that the computer can perform in one second. Each floating point operation is a manipulation, such as addition, subtraction, or multiplication, of two numbers represented by a string of digits.
A gigaflop means one billion (one thousand million, in Britain] floating point operations per second. The International System of Units defines the prefix giga as one billion, tera as one trillion, peta as one quadrillion, and exa as one quintillion.
A supercomputer is one of the fastest large computers available at the time that it is built. That last phrase is really quite important because computer standards change very rapidly. For example, in 1988, Cray Research Corporation introduced the first supercomputer that was able to run at a speed greater than 2 gigaflops, an amazing rate at that time. Today, many inexpensive laptop computers process data faster than that 1988 supercomputer.
Announcements of the new fastest supercomputer come so regularly that it is impossible to say what the fastest computer is as you read these words. In 1998, the fastest speeds were 400 gigaflops. By 2006, IBM had announced its Blue Gene computer had a speed of almost 400 teraflops, a thousand times as fast. In early 2008, Sandia and Oak Ridge national laboratories announced the formation of a joint institute to develop "novel and innovative computer architectures" for exaflop computers, another 2,000-fold increase in computing speed.
So what do they do with the biggest computers out there? Supercomputers work on very complex problems that have a lot of variable parts. Imagine trying to make a model of the whole atmosphere, taking into account each little difference in heating by sunlight all around the world. Atmospheric models use a lot of data and supercomputers process the data points. Models of proteins and how they interact with other molecules in drugs and diseases could not be handled without super-speed processing. Aircraft manufacturers use them to work out the design details of huge jetliners. It always helps to avoid trial-and-error testing with real planes.
One of the motives for looking at new ways to approach super-computing is that, using 2008 technology, the cost of electricity to run an exaflop computer could exceed $10 million per year.
How do magnetic strips on a credit card work?
If you look in your wallet, you will find that all of your credit cards and ATM cards have a long, usually black, rectangle on the back. There is a good chance that your insurance card, library card, and even your driver’s license have similar strips. These are magnetic strips that hold information, such as the card number, that can be interpreted when the card is swiped through a reader. How do these strips work?
The magnetic strip is a thin layer of magnetic material. It is made by imbedding finely powdered iron in plastic and bonding the mix to the card. When the iron particles are exposed to a strong magnetic field, they become tiny magnets themselves. Information, such as the account number, is coded onto the strip by magnetic devices that are similar to the head of a tape recorder. A series of magnetic stripes are formed in the strip. These stripes can be interpreted as a zero or a one, depending on the direction of the North and South Poles.
When you pass the card through a card reader, you slide these magnets in front of coils of conducting wire. The moving magnetic fields create an electric current in the coils. The current is amplified and sent to a computer, which interprets the information.
You have to keep your magnetic cards away from strong magnetic fields. Although the tiny magnets in the strip are fairly stable and can hold their information for years, their information can be easily erased. When the iron particles in the card stripe are exposed to a strong magnetic field, their own polarization will quickly change, effectively removing the stripes and erasing the stored information.
Fast Facts
The technique that is used to bond the magnetic strip to the card is an example of serendipity—the seemingly accidental inspiration that leads to sudden insight. According to Forrest Parry, t he IBM engineer who invented the card, he had become frustrated with every attempt to find an adhesive to bond the magnetic tape to the card. His wife was ironing clothes as he told her about his problem, so she tried attaching the plastic using the heat of the iron, which was at the right temperature to bond the material without destroying it.
"All of the information that man has carefully accumulated in all the books in the world can be written in a cube of material one two-hundredth of an inch wide—which is the barest piece of dust that can be made out by the human eye."
How do retail theft-prevention alarms work?
Retail stores often have a set of tower like structures bracketing the entryway inside the door that set off a shoplifting alarm. If you have ever had a clerk forget to deactivate the alarm tag on a purchase you’ve made, you know that they really work. How can an inexpensive, disposable tag set off the alarm, and how can a clerk turn the tag off?
Electronic article surveillance (EAS) systems use tags attached to an article to determine whether the article has been authorized to leave the store. Most systems use disposable tags that do not have to be removed. Instead, some action is taken to deactivate the tag when an item is purchased so that it does not trip the alarm. Sometimes the tag is actually integrated into the product itself.
Most stores use one of three different EAS technologies: radio frequency (RF), electromagnetic (EM), or acousto-magnetic (AM) systems. The tags, which generally cost no more than a few cents, are not reusable and they are discarded by the consumer after leaving the store.
Most common in the United States are the RF systems, which have a tag containing a miniature electronic circuit and an antenna. These are usually enclosed between two layers of paper about 1′/2 inch square. If you separate the paper you can see the components. The circuit includes a very small coil and a capacitor. The antenna looks like a spiral of thin aluminum foil. One tower beside the door emits radio waves at a specific frequency. When the circuit detects this frequency, it absorbs the energy and emits radio waves at a different frequency, which are detected by the other tower. The tag is deactivated by passing it over a more powerful radio signal that burns out the electronic components.
In Europe, EM systems are more common.The tag that is attached to the item contains a strip of material that absorbs electromagnetic energy. As in the RF system, a radio-wave signal passes between the towers.
When the wave interacts with the strip, the strip absorbs some of the energy of the wave and it becomes magnetized. Once the strip is fully magnetized, it no longer absorbs energy and the system detects the increase in the electromagnetic energy passing between the towers. The strip is paired with a thin piece of magnetic material. To activate the tag, the magnetic material is demagnetized. To deactivate the tag, it is magnetized. The presence of the nearby magnet keeps the absorbing strip magnetized all the time so that it does not send a signal to the detector.
Acousto-magnetic systems, like the other EAS systems, use a radio-wave signal to cause a response by a tag. A flexible material in an AM tag shrinks in response to a magnetic field. This material is paired with a hard magnet that exposes the strip to a magnetic field. When the tag is exposed to the radio waves from the tower, the strip shrinks and expands, resonating like a tuning fork. The resonation sends out a high-frequency sound wave that is detected by the other tower. AM systems can be used in wider doorways than the other EAS systems. The strip is deactivated by demagnetizing the hard magnet.
How does a grocery store scanner work?
They first started to appear on groceries in the 1970s—a series of black lines on a white background. Today barcode labels appear on any package you buy. Every product has a unique label that you run past a laser to bring up the price. What information do these barcodes contain, and how do they work?
Barcodes were originally designed to help grocery stores keep better track of inventory and to make checking out faster. This application has been codified in Universal Product Code (UPC) labels, which were so successful that they have expanded to encompass almost all commercial products. Each UPC label has a series of black lines, some narrow and some wide, on a white background. Beneath the lines, you can also find a series of numbers.
The numbers on the label are a unique code for the product. Every manufacturer that participates in the UPC system pays an annual fee and is assigned an identifying number—the first six digits of the code. The next five digits identify the particular product and package size. The final digit is a check code that is used to confirm that the identifying code has been read correctly.
The lines above the numbers are a code, representing the same numbers in a form that the scanner can recognize. A laser illuminates the bars and the reader detects the pattern of bars, sending the code to a computer that identifies the product. Prices are not encoded in the barcode. Instead, they are stored in the computer, available immediately on identification. This allows the store to adjust prices without relabeling the product.
The check digit on a UPC barcode is a protection against errors. Although scanners seldom misread the code, it does occasionally happen. The check digit is derived by mathematical manipulation of the other 11 digits. If the computer calculates a check number that does not match the digit on the bar, it indicates that the code was not read. This check reduces errors by 90 percent.
Product labels are not the only use for barcodes. The same technology is useful for anything that involves monitoring or tracking. Instead of using an assigned UPC code, other barcode systems use codes that are designed specifically for the purpose. Uses for barcodes include monitoring factory inventories, tracking medical samples in laboratories, following packages from pickup to delivery, and identifying hospital patients. Researchers studying honeybees have even labeled the bees with tiny barcodes to track their comings and goings.
How do radio frequency identification devices work?
In the interest of faster transactions (saving a whole 10 seconds), credit card companies have begun using contactless credit cards. You simply wave the card in front of the reader—no impressions or swiping a strip—and the transaction takes place. Actually, speed is only one consideration. Credit card issuers also believe the cards are safer because the credit card number is never recorded during the transaction. How do credit cards work without any contact with a reader?
Contactless credit cards are only one example of a technology called radio frequency identification (RFID). Instead of a magnetic strip, information is stored in a small chip on the credit card. Inside the reader, an antenna is used to send out a radio wave signal. Inside the chip, a circuit detects the signal and sends out a response containing the identification code that it stores. A receiver in the reader relays the code to a computer, which handles the rest of the transaction.
Contactless credit cards can be hazardous to your wealth. Researchers have found that consumers spend about 15 percent more at locations with con-tactless cards compared to similar locations with traditionally scanned credit cards.
There are two types of RFID tags—passive and active. In a passive tag, the radio signal from the reader provides all the energy needed for the chip to receive and transmit information. These tags never wear out. In an active tag, the chip has a battery to provide power. Active tags can receive and transmit information for longer distances but eventually the battery will wear out, although it may last many years.
The RFID tag uses information in the same way as a barcode or magnetic strip. It functions only as an identifier. Any other information is stored in a computer that is accessible to the reading device. RFID devices have several advantages over barcodes and magnetic strips: passive tags work several feet away from the reader, active devices even farther; they do not make contact with anything so they don’t wear out; they can be read very quickly; and many tags can be read at the same time by a single reader.
RFID tags come in many sizes and shapes. The smallest are barely as large as a grain of sand. In bulk production, their cost, currently as low as a few cents, is expected to drop to less than a penny apiece. It is possible that UPC labels will eventually be replaced by RFID devices incorporated into every product. An entire cart of products could then be scanned simply by rolling the cart in front of a reader.
The tags are already used for a wide range of purposes. In addition to credit cards and product labeling, they have been inserted beneath the skin of pets for identification of lost animals, built into expensive musical instruments, and used to track warehouse inventories and open locked doors. RFID tags placed on the windshields of cars allow traffic to flow smoothly through toll plazas, subtracting the toll from each account as a tag identifies itself to the overhead reader.
How do solar cells convert sunlight into electrical energy?
Driving down the highway, you often see signs indicating temporary road conditions, such as construction. Frequently, the sign is accompanied by a pole topped by a flat plate, facing upward. This plate is a solar cell, which charges a battery during the day so that the sign can be lighted at night. How does a solar cell produce an electric current?
A solar cell, or photovoltaic (PV) cell, converts the energy from light into an electric current when the light interacts with atoms in the cell. Although the first photovoltaic cells were built in 1954, they were very expensive for ordinary use. Until the 1980s, these cells were used mostly to provide power to spacecraft because the ability to produce power without using heavy fuels made up for their cost. Advances in efficiency of the cells and significant cost reductions in producing materials now make them feasible for a number of applications, including providing power for buildings.
A semiconductor is a solid material whose electrical conductivity is between that of a conductor and an insulator. In general, the conductivity of a semiconductor can be changed by changing its temperature or modifying it by doping with other elements. Most semiconductors used for electronics applications are made of silicon, germanium, or compounds of one of these elements.
All PV cells are made of semiconductors, most commonly silicon. In a silicon crystal, each atom is bonded to the atoms around it by sharing electrons. When an impurity such as phosphorus, which has more electrons than silicon, is added in small amounts (about one atom out of every million atoms), it has an electron that is not shared with another atom. Adding an impurity to the silicon is called doping. If the impurity has nonshared electrons, the doping is called n-doping (n for negative, the charge of an electron). If the silicon is doped with an element such as boron, that is called p-doping (positive). Boron has fewer electrons than silicon and it provides a space where an electron could be shared by two atoms.
If a layer of n-doped silicon and a layer of p-doped silicon are placed together, some of the electrons move from the n side to the p side. However, as the electrons fill spaces a boundary forms. The two semiconductors become a diode. Electrons will only move past the boundary if they have a certain amount of energy. That’s where light comes in. When light strikes the n-doped semiconductor, electrons of the doping atoms absorb energy and begin to move across the boundary to the p-doped semiconductor.
This cannot continue for very long, though, because a negative charge will build on the p side and repel electrons trying to cross the boundary. However, if you connect the two sides of the diode with an external wire, the energetic electrons can continue moving through the wire and back to the (now positively charged) inside.
An electric current is simply a flow of electrons in a conductor, so you have created an electric current. The energy of the moving electrons can be used to turn on a light, run a motor, or charge a battery for use later. This current will continue to flow as long as light adds energy to the electrons on the n side of the cell. The amount of electric current produced by the PV cell is directly proportional to the amount of light that strikes it.
Articles about solar cells sometimes state that they "convert photons of light into electrons." This is a misconception. The photon of light is absorbed by an atom and the added energy can cause an electron to leave the atom. The electron already existed, however, so no electron was created by the process. The light simply added energy to the electron.
How do digital cameras take pictures?
How often do you take film to the drugstore to be developed? If you are like most people, you no longer use film cameras, having adopted a digital camera instead. Photography is a field that has been drastically affected by the development of inexpensive computers. How do digital cameras differ from film cameras?
In general, the two types of cameras work the same way: light reflected from objects in front of the camera is captured through a lens and focused on a detector that records an image of the objects. The difference lies in the type of detection used to convert the light into a recorded image. On film, fine grains of light-sensitive chemicals change when they are exposed to light. Once the film is developed, these changes are permanent and the film cannot be reused.
In a digital camera, light strikes an array of electronic devices, called charge coupled devices (CCD), which are sensitive to light. When light strikes a CCD, electrons flow and cause a charge to accumulate. A computer then records the charge on each CCD element digitally and combines them to form a picture. The response of each CCD represents one tiny dot, called a pixel, in the final picture.
However, a CCD does not respond to color in the same way as the chemicals in film. Because each CCD is either on or off and it responds to any light that strikes it, camera makers have to trick them. Color filters are placed above each electronic element. The filter allows only one color of light to pass, so each pixel responds only to its own color. The computer assigns that color to the pixel representing that CCD. Just as the image on a computer monitor is made of an array of tiny colored dots, a digital photo consists of an array of colored dots. Every CCD response makes up one pixel of the final photograph.
Early digital cameras were not able to produce images whose quality equaled that of film cameras. However, as the size of the CCDs becomes smaller and their efficiency is improved, camera manufacturers are able to add more pixels as well as improve their performance. The quality of a digital photograph depends on the number of pixels, the type of CCD used, and the quality of the camera lenses that focus the image on the CCD array. Most digital cameras today are able to make a print that has a resolution that is as good as a 4"x5" print from a film camera. The top-of-the-line digital cameras are approaching the resolution of the best film cameras, although many professional photographers prefer to use film for some types of photographs.
Fast Facts
The resolution of a digital camera is measured in the number of pixels that it has, which corresponds to the number of CCD elements. Cameras with a resolution of fewer than 250,000 pixels are essentially toys. Between 250,000 pixels and 1,000,000 pixels (1 megapixel), the pictures are suitable for snapshots or website photos. For printing photographs, you should have about 1 megapixel for 3"x5" photos, 2 megapixels for good 4"x5" photos, and 4 or more megapixels for larger prints. Professional photographers use cameras with very high-quality lens systems and about 11 megapixels to produce photographs whose resolution is similar to that of large-format film.
Why are there places that a cell phone does not work?
Cell phones are generally a reliable means of communication—so reliable that many people have abandoned land lines and use their cell phone exclusively. Even so, there are always those annoying moments when the call disappears and occasional places where there is no signal. Why do dead spots exist where a cell phone does not work?
First, let’s take a look at how cell phones work. Mobile wireless phones have been around since the 1940s. The early systems used a few towers, generally one per metropolitan area, which sent and received signals as radio waves. The tower communicated to the mobile phones by radio and then sent the transmission on using regular land lines. By broadcasting strong signals at a number of different frequencies, these towers could handle tens or hundreds of calls at a time. When calls are expensive and mobile phones are rare, this works, but the number of available frequencies is limited, so there is no room for increased demand.
The solution to the problem of limited availability was the cell concept. In a cellular system, there are many towers within an area that once had only a single tower. Each tower covers a much smaller area, known as a cell. When you make a call on a cell phone, you communicate on a frequency that may be in use by callers throughout a city, although you are the only caller using it in a particular cell.
Fast Facts
A satellite system, the Iridium network, was started in 1998 to provide cell phone coverage worldwide without any dead zones. The plan was to have 77 satellites covering the whole earth. However, the satellite network was extremely expensive and ground-based networks grew rapidly, so the system was unable to compete in price. The company filed for bankruptcy less than 10 months after launching the system. An investment that cost about $6 billion was sold for $25 million. Today the system functions with 66 satellites, primarily serving the U.S. Department of Defense, large corporations, and very remote scientific research stations.
One big advantage of a cellular phone system comes from computers that can monitor the system and track your call as you move from one cell to another. Usually, you are transferred from one tower to another with no noticeable change. Computerized systems can also handle digital signals which are much more efficient for transferring data. As the number of towers has increased, the number of calls each tower can handle has also increased to the point where it seems that everyone is always on the phone.
Another advantage of closely spaced cell towers is that cell phones need a much less powerful signal. Some older mobile phones had a battery pack the size and weight of a brick. Today you can carry a phone in your shirt pocket and still have room for a business card holder. The difference is a combination of miniaturization of electronic components and the reduced need for battery power to send a strong signal.
There is a downside to a lower power output, though. Early cell phones broadcast a strong signal that could be detected by a tower 50 miles or more distant. Today’s cell phones are designed to operate within a few miles of a tower. In a rural area, you may be too far from a network tower and therefore out of the coverage area. Also, the weaker signals are more likely to be blocked by hills, buildings, or even dense foliage. Dead zones can therefore occur even in places where there should be coverage. Wireless service providers are continually adding towers and antennas, as well as improving transmission systems.
