2DIGITAL DEVICES

sectionA

DEVICES BASICS

WHAT’S InSIde all these digital
devices that we use? Whether you’re oper- ating your trusty laptop or figuring out how to safely clean your smartphone screen, it is useful to have some background about the components of digital devices and how they work. Section A looks at digital devices from the inside out, first focusing on characteristics common to all digital devices, and then drilling down to circuits and chips.
Objectives
◗ Draw a diagram showing the IpOS model of activities characteristic of computers.
◗** Describe the stored program concept and why it distinguishes computers from other simpler and
less versatile digital devices. **
◗** State which of the following are application software and which are system software: iOS,
Windows, Microsoft Word, Android, powerpoint. **
◗ list three terms that are commonly used alternatives for “integrated circuits.”
◗ Explain why semiconductors are the materials used for integrated circuits.

computer input output process data
central processing unit microprocessor
memory storage computer program software stored program
application software apps system software operating system development tools integrated circuit semiconductors
system board form factor system unit
oleophobic lithium ion discharge rate

◗ Identify the microprocessor on a system board.
◗ Identify the components of a typical device that has a component, clamshell, or slate form factor.
◗ list four mistakes to avoid when cleaning a digital device.
◗ Describe what to do if liquid is spilled on a device.
◗ Explain how to care for a touchscreen.
◗ list six steps to take to increase battery life and lifespan.
COMPUTERS
Pixar's huge server array that renders 3D animated movies and the tiny iPhone you can hold in your hand have more in common than you might think. These devices, along with mainframes, desktops, tablets, ebook readers, and game consoles, are all based on computer technology. Understanding the classical definition of a computer provides a useful pic- ture of what all these devices have in common.
◗What is a computer?Most people can formulate a mental picture of a computer, but computers do so many things and come in such a vari- ety of shapes and sizes that it might seem difficult to distill their common characteristics into an all-purpose definition. At its core, a computer is a multipurpose device that accepts input, processes data, stores data, and produces output, all according to a series of stored instructions.
lnput is whatever is typed, submitted, or transmitted to a computer. Output is the result produced by a computer. lnput and output can be handled by components contained within the computer or by add-on, such as keyboards and printers, that are attached to the computer with cables or connected wirelessly.
Computers process data by performing calculations, modifying docu- ments and pictures, drawing graphs, and sorting lists of words or numbers. Processing is handled by the computer's central processing unit (CPU). The CPU of most modern computers is a microprocessor, which is an electronic component that can be programmed to process data.
Computers store data and the software that processes data. Most computers have temporary holding areas called memory in addition to long-term storage housed on hard disks or flash drives. Figure 2-1 illus- trates the lPOS (input, process, output, store) activities characteristic of computers.

Terminology
The word computer has been part of the English language since 1613; but if you look in a dictionary printed before 1940, you might be surprised to find a computer defined as a person who performs calculations. Prior to 1940, machines designed to perform calculations were usually referred to as calculators and tabulators, not computers. The modern definition and use of the term computer emerged in the 19405, when the first electronic computing devices were developed.
◗What’s so significant about a computer’s ability to store instructions? The instructions that tell a digital device how to carry out processing tasks are referred to as a computer program, or simply a program. These programs form the software that sets up a computer to do a specific task. When a computer “runs” software, it performs the instructions to carry out the task. The first computers were “programmed” to perform a specific task by connecting wire circuitry in a certain way. Changing tasks meant rewiring the circuits. The term stored program means that a series of instructions for a computing task can be loaded into a computer’s memory. These instructions can be replaced easily by a different set of instructions when it is time for the computer to perform another task. This ability to switch programs makes computers multipurpose devices (Figure 2-2).

QUICKCHECK
The stored program concept turns computers into ___________.

calculators
smartphones
multipurpose devices
software
The stored program concept allows you to use a computer for one task, such as word processing, and then easily switch to a different type of computing task, such as editing a photo or playing music. It is the single most important characteristic that distinguishes computers from other simpler and less versatile digital devices, such as digital clocks, calculators, and cameras.

QUICKCHECK
◗What kinds of software do computers run? Computers run three main types of software: application software, system software, and development tools (Figure 2-3). A computer can be applied to many tasks, such as writing, number crunching, video editing, and online s hopping. Application software is a set of computer programs that helps a person carry out a task. Application software is sometimes referred to as an app. Whereas application software is designed to help a person carry out a task, the primary purpose of system software is to help the computer system monitor itself in order to function efficiently. An example of system software is a computer operating system (OS), which is essentially the master controller for all the activities that take place within a computer. Development toolsare used for creating software applications, Web sites, operating systems, and utilities. Examples of development tools include computer programming languages, such as C++, and scripting languages, such as HTML.

ClRCUlTS AND CHlPS
The first computers were closet-sized devices filled with Wires, vacuum tubes, transistors, and other bulky components. As digital electronics evolved, components became smaller and smaller. Open up a digital device. You won't see clumps of Wires and gears. lnstead, you'll see small circuit boards and integrated circuits. These tiny components are the essence of digital electronics.
What are digital electronics? Digital electronics represent data bits as electrical signals that travel over circuits in much the same way that electricity flows over a wire when you turn on a light switch. To represent data, such as 01101100, high-voltage signals are used for 1 bits, and low- voltage signals are used for 0 bits. All the calculations performed by digital devices take place in a maze of electronic circuitry (Figure 2-4).

QUlCKCHECK ln Figure 2-4, the fiery bit
. represents 3 1 O'Q) . is heading toward a resistor
O . is a low-voltage signal

represents 3 0
This little circuit is composed of electrical pathways (lines), tran— sistors (circles), and resistors (rectangles). The electronics for digital devices require millions of similar circuits. Today, this circuitry is condensed into integrated circuits.

◗What's an integrated circuit? An integrated circuit (lC) is a set of microscopic electronic components etched onto a thin slice of semi- conducting material. The terms computer chip, microchip, and Chip are commonly used to refer to integrated circuits. Some integrated circuits are devoted to collecting input, while others might be devoted to processing tasks, output, or storage. The first computer chips contained fewer than 100 miniaturized components, such as resistors and transistors, The chips for today's digital devices contain billions of transistors, Semiconductors, such as silicon and germanium, are substances with properties between those of a conductor (like copper) and an insulator (like wood). To fabricate a chip, the conductive properties of selective parts of the semiconductor can be enhanced to essentially create min- iature electronic pathways and components, such as transistors, as shown in Figure 2-5.

QUlCKCHECK
There is an abundant supply of materials for fabricating semiconductors because:

They are made from purified silicon (sand).
They are basically insulators made from wood.
◗ Aren't chips black? lntegrated circuits are packaged in protec- tive carriers that very in shape and size. Figure 2-6 illustrates some chip carriers, including small rectangular DlPs (dual in-line packages) with caterpillar-like Iegs protruding from a black, rectangular body, and pin- cushion-like LGAS (land-grid arrays).

◗How do chips fit together? The electronic components of most digital devices are mounted on a circuit board called a system board, motherboard, or main board. The system board houses all essential chips and provides connecting circuitry between them. Figure 2-7 illustrates the main chips on the front and back sides of a laptop system board.

TRY lT!
The chips on a circuit board have identifying numbers that you can look up online. Suppose you've opened the system unit of a Microsoft Surface tablet and vou're looking at a chip labeled Atmel MXT154E. Can you find out what it does?
COMPONENTS
When you acquire a new digital device, your first step is to locate the power button and all the other hardware components. The devices we use today have a fairly predictable collection of features, depending on the device's form factor.
◗What is a form factor? in the computer industry, the term form factor refers to the size and dimensions of a device or components, such as circuit boards and system units. The term system unit is tech speak for the part of a digital device that holds the system board. it can apply to the body of a smartphone or laptop, as well as to the tower unit of a desktop computer. Digital devices are available in all sorts of form factors; some of the most popular include component, clamshell, and slate.
◗What are the features of a component system?
Acomponent device is composed of various standalone parts, such as a display unit, system unit, and keyboard. Components can be connected using cables or wireless signals. Most of the first personal computers were component systems. Today, this form factor is much less popular because of the eﬀort required to assemble the components. Figure 2-8 illustrates the hardware features of a typical component system.

QUlCKCHECK
How many on/off buttons would you expect on a component system like the one in Figure 2-8?

One on the system unit
One for each standalone device
One on the system unit and one on the display device
◗What are the features of a clamshell device? Clamshell devices have a keyboard as the base and a screen on the hinged cover. The system unit on these devices contains all of the basic components required for input, processing, storage, and output (Figure 2-9).

◗What are the features of a slate device?
Devices configured in the slate form factor feature a touchscreen that covers most of the device's surface. The screen can display a virtual keyboard for text Check out the devices that and numeric input. An additional control, such as a Home button or a you own. Can you find all of circular control pad, is featured on some slate devices. The system unit the components listed in the also includes controls for commonly used features, such as volume and figures? airplane mode (Figure 2-10).

QUICKCHECK
How many components are typically housed on the top half of a clamshell device?

One
Two
Three
Four
TRY IT!

Check out the devices that you own. Can you find all of the components listed in the figures？
MAinTenAnCe Digital devices can be costly. You can extend their life with a bit of regular maintenance. There are four components of digital devices that require maintenance: the system unit, keyboard, screen, and battery.
◗How do I start? Before you undertake any maintenance, turn the device off—that’s off, not just asleep—and disconnect any power cables. Doing so will prevent random screen swipes or key presses from altering your device settings.
◗Which cleaning products are safe to use? The products you can use depend on the component you are cleaning. What might work well to scrub out stubborn stains on the system unit case could permanently cloud or scratch your touchscreen. Always follow the manufacturer’s advice for cleaning procedures and products (Figure 2-11).

◗What kind of maintenance does the system unit require? Basic system unit maintenance is simple. You want to keep the unit clean, prevent it from overheating, shield it from damage, and protect it from electrical surges (Figure 2-12).

◗How can I safely clean and disinfect a touchscreen? Touchscreens collect fingerprints and are a breeding ground for bacteria, so it is a good idea to clean them periodically. Many touchscreens are made from Gorilla Glass, which is designed to resist scratching and cracking. Damaged screens can be replaced, but that can cost close to $100, so a few preventive measures may help you avoid costly repairs. A plastic screen protector is the first line of defense against scratches and cracks. These films can be cleaned using water and a soft cloth, or a disinfecting wipe. When the screen protector gets grubby, simply peel it off and replace it with a new one.
QUICKCHECK
What is the first step for hardware maintenance?

Wipe it with a soft cloth.
Remove the screen protector.
Turn the device off.
Vacuum the fan vents.
Without a screen protector, you will have to carefully clean the screen itself. Many touchscreens have an oleophobic coating designed to repel the oils deposited by fingertips. When alcohol is used to clean these screens, each application degrades the coating. Non-alcohol wipes are available, or use eyeglass cleaner.

◗What about my keyboard? Keyboards quickly build up grime, gather dust, and collect crumbs. To start the cleaning process, turn the keyboard upside down and shake it gently to dislodge debris. Most manu- facturers suggest using an antibacterial wipe to clean key surfaces. Take a moment to test the cleaning product on a small unnoticeable spot just to make sure it will not discolor the keys or leave a residue. Use cotton swabs to clean between the keys.
◗What is the best way to clean up spills? Liquids and elec- tronics don't mix. if you spill liquid on a device, turn it off immediately. With luck, that step will prevent electrical shorts that would permanently damage circuit boards. Once the device is oﬀ, you can assess the dam- age. if the spill is water, dry off the device, shake out the moisture, and set it in a warm, dry place where there is good air Circulation. Afan or hair dryer set on low can help drive out moisture. Allow the device to dry for at least 72 hours.
Sticky spills are another matter. if the goo has penetrated the interior of the device, it is best to leave the cleanup to a professional. if you think the spill only affected the surface, you can wipe the device with clean water and allow it to dry for 24 hours (Figure 2-13).

◗How do I maintain the battery for a device? You know how it goes. it happens to everyone. The battery on your device dies just when you really need it. Battery life is the time your device operates before it must be recharged. Battery lifespan is the amount of time a bat- tery lasts until it must be replaced. Good maintenance extends the life of your battery and its lifetime, so your digital devices are ready when you need them.
Most of today's battery-powered digital devices contain a lithium ion (Li-ion) battery. Unlike batteries of the past, Li-ion batteries contain no toxic compounds and operate efficiently, but they are sensitive to heat.
Li-ion batteries can occasionally overheat, and in the worst case, they can explode. Most devices today contain circuitry to prevent heat-triggered damage, but smart consumers don’t operate devices that are hot to the touch. Batteries have a discharge rate at which they lose charge even when not in use. The discharge rate for Li-ion batteries is quite low—about 1.5% per month—so the batteries in your devices basically discharge only as they are used. Device manufacturers often advertise battery watts per hour (Wh). A 60 Wh battery will last 60 hours if it expends 1 watt per hour. A typical laptop uses about 30 watts per hour, however, so a 60 Wh battery can power the device for two hours (60 Wh ÷ 30 watts = 2 hours). Some applications require more battery power than others. Locationbased apps that keep track of your whereabouts are constantly using extra power to check cell towers or Wi-Fi networks. Push applications, such as autoretrieving email, make your device continually check for new messages. To extend battery life, disable these kinds of apps when you are not using them. Figure 2-14 summarizes good practices for charging and using Li-ion batteries.

sectionB

DEVICES OPTION

ENTERPRlSE COMPUTERS
At one time, it was possible to define three distinct categories of computers. Mainframes were housed in large, closet-sized metal frames. Minicomputers were smaller, less expensive, and less powerful, but they could support multiple users and run business software. Microcomputers were clearly diﬀerentiated from computers in other categories because they were dedicated to a single user and their CPUs consisted of a single micro- processor chip.
Today, microprocessors are no longer a distinction between computer categories because just about every computer uses one or more micropro- cessors as its CPU. The term minicomputer has fallen into disuse, and the terms microcomputer and mainframe are used with less and less frequency.
◗What are the most powerful computers?
Today's most power- ful computers include supercomputers, mainframes, and servers. These devices are generally used in businesses and government agencies. They have the ability to service many simultaneous users and process data at very fast speeds (Figure 2-15).
Supercomputers. A computer falls into the supercomputer category if it is, at the time of construction, one of the fastest computers in the world. Because of their speed, supercomputers can tackle complex tasks that just would not be practical for other computers. Typical uses for
supercomputers include breaking codes, modeling worldwide weather systems, and simulating nuclear explosions.
Computer manufacturers such as lBM, Cray, and China's NRCPC have in recent years held top honors for the world's fastest computer. Supercomputer speeds are measured in petaﬂops (PFLOPS). One petaflop is an astounding 1,000,000,000,000,000 (quadrillion) calculations per sec- ond. That's about 20,000 times faster than your laptop computer.
Mainframes. A mainframe computer (or simply a mainframe) is a large and expensive computer capable of simultaneously processing data for hundreds or thousands of users. lts main processing circuitry is housed in a closet-sized cabinet like the one shown at left; but after large components are added for storage and output, a mainframe installation can fill a good- sized room.
Mainframes are generally used by businesses and government agencies to provide centralized storage, processing, and management for large amounts of data. For example, banks depend on mainframes as their com- puter of choice to ensure reliability, data security, and centralized control. The price of a mainframe computer typically starts at several hundred thou- sand dollars and can easily exceed $1 million.
Servers. The purpose of a server is to "serve" data to computers con- nected to a network. When you search Google or access a Web site, the information you obtain is provided by servers. At ecommerce sites, the store's merchandise information is housed in database servers. Email, chat, Skype, and online multiplayer games are all operated by servers.
Technically, just about any computer can be configured to perform the work of a server. However, computer manufacturers such as lBM and Dell offer devices classified as servers that are especially suited for storing and distributing data on networks. These devices are about the size of a desk drawer and are often mounted in racks of multiple servers.

PERSONAL COMPUTERS
A personal computer is designed to meet the comput- ing needs of an individual. These computers were originally referred to as microcomputers. Personal computers provide access to a wide variety of computing applications, such as word processing, photo editing, email, and lnternet access.
The term personal computer is sometimes abbreviated as PC. However, PC can also refer to a specific type of personal computer that descended from the original lBM PC and runs Windows software. in this book, PC refers to lBM PC descen- dants. it is not used as an abbreviation for personal computer.
◗What are the options for personal computers?
Personal computers can be classified as desktop, portable, or mobile devices. The lines that delineate these categories are sometimes a bit blurry, but the general characteristics of each category are described below and common configurations are shown in Figure 2-16.
Desktops. A desktop computer fits on a desk and runs on power from an electrical wall outlet. The keyboard is typically a separate component connected to the main unit by a cable. A desktop computer can be housed in a vertical case or in a horizontal case. in some modern desktops, called all-in-one units, the system board is incorporated into the display device. Desktop computers are popular for oﬃces and schools where portability is not important. Their operating systems include Microsoft Windows, macOS, and Linux. The price of an entry- level desktop computer starts at $500 or a bit less.
Portables. A portable computer runs on battery power. lts screen, keyboard, camera, storage devices, and speakers are fully contained in a single case so that the device can be eas- ily transported from one place to another. Portable computers include laptops, tablets, and smaſtphones. Laptops.
A laptop computer (also referred to as a note- book computer) is a small, lightweight personal computer designed like a clamshell with a keyboard as the base and a screen on the hinged cover. Most laptops use the same oper- ating systems as desktop computers, with the exception of Chromebooks, which use Google's Chrome OS as their oper- ating system.
A Chromebook is a special category of laptop, designed to be connected to the lnternet for most routine computing activi- ties. Chromebook owners use Web-based software and store all their data in the cloud rather than on a local hard disk. Chromebooks use a standard clamshell form factor, so they look very much like a laptop. Their sub-$300 price tags are attractive to consumers who primarily browse the Web and use Web-based apps.

Tablets. A tablet computer is a portable computing device featuring a touch-sensitive screen that can be used for input as well as for output. Tablet computers use specialized operating systems, such as iOS and Android, or special operating system modes, such as Windows 10 Tablet mode. Some models support cell phone network data plans but require apps such as Google Voice or Skype for voice calls.
A slate tablet configuration is basically a screen in a narrow frame that lacks a physical keyboard (although one can be attached). The Apple iPad and Samsung Galaxy Tab are popular slate tablets. A 2-in-1 (or convertible tablet) can be operated using its touch-sensitive screen or with a physical keyboard that can be folded out of the way or removed.
Smartphones Smartphones are mobile devices that have features similar to tablet computers, but also provide telecommunications capabilities over cell phone networks. They can make voice calls, send text messages, 1and access the lnternet. Unlike a basic mobile phone, smartphones are 1. programmable, so they can download, store, and run software.
Smartphones are the most commonly used digital device in the world. A smartphone features a small keyboard or touchscreen and is designed to fit into a pocket, run on batteries, and be used while you are holding it in your hands (Figure 2-17).

Smartphones are equipped with built-in speech recognition that allows you to ask questions and control the device using spoken commends. Smartphones also include GPS capability so that apps are able to provide location-based services such as a route navigation map or a list of nearby restaurants.
Smartphones evolved from basic cell phones and PDAs. A PDA (personal digital assistant) was a handheld device used as an electronic appointment book, calculator, and notepad. Modern smartphones include a similar suite of applications, but they also have access to a huge variety of mobile apps that help you calculate tips, play your favorite music, and entertain you with games.
The operating systems for smartphones are similar to those used for tab- let computers. iOS is used on the iPad and iPhone. Microsoft Windows 10 Mobile is used on smartphones that oﬀer a similar user experience as Windows laptops. The Android operating system used on Samsung tab- lets is also used for Samsung Galaxy and Motorola Droid smartphones.
TRY IT !
How many digital devices do you own? Which do you use most often? Make a list of your devices and their serial numbers, and tuck it away in a safe place in case one of your devices is lost or stolen.
NlCHE DEVlCES
The list of digital devices is long. Many devices, such as fitness track- ers, cameras, and handheld GPSs, are dedicated to specific tasks. Other devices perform a wider variety of tasks.

◗What about other digital devices? Niche devices all have one thing in common: They contain a microprocessor. Some of these devices, such as smartwatches and fitness trackers, can be classified as wearable computers. Which of the devices in Figure 2-18 do you own?
Raspberry Pi. Afull computer system unit that is just a tad larger than a deck of cards, the Raspberry Pi can be connected to a keyboard and screen for a full computer experience. These little powerhouses cost less than $50 and provide an inexpensive platform for experiment- ing with programming, robotics, and just about any creative computer application you can imagine.
Game consoles. Devices for playing computer games include Sony's PlayStation, Nintendo's Wii, and Microsoft's Xbox. They fea- ture powerful processing capability and excellent graphics, but they are generally used for dedicated game playing and streaming videos rather than running application software.
Portable media players. Media players, such as the iPod Touch, revolutionized the music industry by providing consumers with a handheld device that can store and play thousands of songs. These devices are controlled by touchscreens or simple click-wheel mecha- nlsms.
Smartwatches. Watches and clocks were some of the first devices to go digital. Mass produced in the 19703 with a price as low as $10, these watches were limited to time and date functions. in 2013, Samsung, Google, and Qualcomm introduced a new breed of digital watch. Dubbed smartwatches, these multifunction devices can include a camera, thermometer, compass, calculator, cell phone, GPS, media player, and fitness tracker. Some smartwatch functions are onboard the device, whereas other functions require access to the lnternet or to the wearer's smartphone.
Activity trackers. To monitor activity throughout the day, you can wear a fitness tracker. These devices, worn on the wrist or clipped to a pocket, monitor your steps and heart rate. They can calculate calo- ries, graph your fitness achievements, and share information with your Facebook friends.
Smart appliances. Modern refrigerators, washing machines, and other appliances are controlled by integrated circuits called microcontrollers that combine sensors with processing circuitry. Microcontrollers can monitor energy eﬃciency, offer programmed start times, and may be controlled remotely from a smanphone or laptop.

◗What are the pros and cons of the most popular consumer devices? The most popular digital devices are desktops, lapt0ps, tablets, and smartphones. Figure 2-20 can help you choose the one that best meets your needs.

◗How important is compatibility? Suppose that you want to work on some assignments at home using the same software provided by your school lab. Maybe you want to transport data back and forth between your job and home. Or, perhaps your children want to use a computer at home that is similar to those they use at school. Computers that operate in essentially the same way and use the same software are said to be compatible. They can also be described as having the same “platform.” To assess whether two computers are compatible, check their operating systems. Computers with the same operating systems can typically use the same software and peripheral devices. Figure 2-21 provides an overview of popular platforms. You’ll learn more about operating systems in a later module.

QUICKCHECK Do Apple and Android tablets use the same software and apps as laptops? a. Yes b. No
◗Should I stick to one family of devices? As you can see from Figure 2-21, operating systems and the devices that use them are grouped into families. Apple produces macOS and iOS. Microsoft produces Windows and Windows Mobile. The open source community produces Linux for desktops and servers; and with the support of Google, it produces Chrome OS and Android. The operating systems within a family have similarities in the way they look and function. So if you are familiar with macOS on your laptop, then you might find it easier to work with an iPhone rather than an Android phone. Working within an operating system family can have other benefits. For example, if you are storing your photos, documents, and other data in Apple’s iCloud, you’ll have easier access to them from devices running iOS and macOS than from a device running Windows. Finally, you might find that synching and backing up data between devices is easier if they have operating systems from the same family.
Terminology Desktops and laptops that run Windows are sometimes referred to as PCs. Computers that run macOS are referred to as Macs.
◗What can I expect to pay for a personal device? The price tag for a smartphone is $200–$900, whereas tablet computer prices range from $200 to $1,200. Desktop and laptop computers usually cost a bit more, with price points roughly grouped into three categories: above $1,200, $500– $1,200, and under $500. Computers priced above $1,200 contain one or more fast processors, a generous amount of RAM, and a copious amount of disk space. These computers contain state-of-the-art components and should not have to be replaced as quickly as less expensive computers. Computer game enthusiasts and anyone planning to work extensively with video editing, graphics, and desktop publishing are likely to require a high-end computer. A majority of buyers select desktops and laptops that retail for between $500 and $1,200. These popular computers lack the flashy specifications of their state-of-the-art cousins but provide ample computing power to meet the needs of an average user. In the computer industry, the equivalent of a compact car is a sub-$500 computer. The technology in these computers is usually a year or two old, and you can expect reduced processor speed, memory capacity, and drive capacity. You might have to replace a budget computer sooner than a more expensive computer, but it should be serviceable for typical applications.
◗What are the factors that have the biggest effect on device prices? A microprocessor is one of the most expensive components in a digital device. The newest, fastest microprocessor is likely to add several hundred dollars to the price tag. Memory is another factor that affects price. For example, doubling the amount of memory in a smartphone could raise the cost from $199 to $299. Large screens cost more to manufacture and raise the price of digital devices. An iMac—Apple’s version of an all-in-one desktop unit—with a 27-inch screen costs $700 more than the 21-inch version. For laptops, size and weight make a difference in price. Thinner and lighter laptops are priced higher, not necessarily because they cost more to manufacture, but because they are more desirable to consumers.
Try iT! Visit the Dell Web site. What is the price of the least expensive desktop computer?
QUICKCHECK The majority of desktop and laptop buyers spend how much on a computer? a. $100–$250 b. $250–$500 c. $500–$1,200 d. $800–$1,500

◗How can I make sense of all the jargon in computer ads? Computer ads are loaded with jargon and acronyms, such as RAM, ROM, GHz, GB, and USB. You’re sure to spot lots of this computer lingo in ads like the one in Figure 2-22. The remaining sections of Module 2 delve into specifications for digital components. You’ll see how these components work and how they affect the way you work. By the end of Module 2, you should be able to understand the terminology in computer ads and use your knowledge to evaluate various digital devices.

sectionC

PROCESSORS And MEMORYSECTION

MiCrOPrOCeSSOrS
A microprocessor is an integrated circuit designed to process instructions. It is the most important, and usually the most expensive, component of a digital device. The specifications for a microprocessor include the manufacturer’s name and the chip model.
◗Which processors are popular for desktops and laptops? Intel Corporation is the world’s largest chipmaker and supplies a sizeable
percentage of the microprocessors that power desktops and laptops. In 1971, Intel introduced the world’s first microprocessor—the 4004. Intel’s 8088 processor powered the original IBM PC, and chips in Intel’s 8086 family powered subsequent models of PCs manufactured by IBM and other companies. The 8086 chip family set the standard for processors used in today’s desktop and laptop computers, as well as servers. This standard is sometimes referred to as x86 because it includes chip models that originally ended in 86, such as the 8086, 80286, and 80386. Modern processors no longer follow Intel’s original numbering sequence, but x86 is still used when referring to the modern descendants of the 8086. Processors found in today’s desktops and laptops are x86 compatible, such as the Intel i3, i5, and i7 microprocessors (Figure 2-23), as well as Athlon and A-series processors manufactured by AMD.

◗Which processors are popular for tablets and smartphones? Whereas processors based on x86 technology are inside just about all desktop and laptop computers, processors based on ARM technology dominate tablet computers and smartphones. ARM technology was originally designed by ARM Holdings, a British technology company founded by Acorn Computers, Apple Inc., and VLSI Technology. Today, ARM processors are designed and manufactured by companies that include NVIDIA, Samsung, and Nintendo. ARM-based processors are energy efficient—an important characteristic for devices that run primarily on battery power. ARM processors are found in Microsoft’s Surface tablets, Apple’s iPads and iPhones, and Samsung’s lineup of Galaxy phones. The processors go by brand names such as Cortex and Apple A10. For Surface 2-in-1 tablet computers, Microsoft uses Core M2 processors specially designed for low-power mobile devices.
QUICKCHECK What does x86 mean? a. It is the model of an Intel chip. b. It designates low-power chips suitable for tablets and smartphones. c. It is used to refer to a standard family of processors used in most desktop and laptop computers. d. It means the chip was manufactured by Intel.
QUICKCHECK Which processor would you be likely to find in an iPhone? a. Intel x86 b. ARM c. Intel Core M3 d. 8088

◗Which microprocessor is best? The microprocessor that's best for you depends on your budget and the type of work and play you plan to do. The microprocessors marketed with the current crop of desktops and laptops can handle most business, educational, and entertainment applica- tions. You'll want to consider the fastest processor oﬀerings if you engage in processing-hungry activities, such as ZD animated computer games, desk- top publishing, multitrack sound recording, and video editing.
◗What microprocessor is in my favorite device? if you know the make and model of a digital device, you can generally find processor specifications by searching online. For example, searching for processor speciﬁcations iPhone 7 reveals that the phone contains an A10 chip with 64-bit architecture.
Although phones and tablets require an online search, desktops and lap- tops oﬀer an easier way to discover exactly what's inside (Figure 2-24).

◗HOw PROCESSORS WORk
To appreciate the microprocessor specifications in your digital devices, it is handy to have a little background on how processors work. This key technology is quite fascinating in its ability to perform an astounding variety of tasks based on a set of really simple instructions.
◗What is the significance of microprocessor instruction sets? Microprocessors are hard-wired to perform a limited set of activities. This collection of preprogrammed activities is called an instruction set. Instruction sets are unique to processor families. x86 processors use a different instruction set than ARM processors. That is one reason why a game designed to run on a smartphone with an ARM processor cannot directly run on your laptop with its Intel i7 processor.
◗What is in an instruction set? An instruction set contains a collection of instructions for actions that the circuitry in a microprocessor can perform. The ARM instruction set contains about 35 instructions, whereas the x86 set includes more than 100 instructions. Each instruction carries out a seemingly insignificant task, such as moving a number from computer memory into the processor or comparing two numbers to see if they are the same. Only when millions of these instructions are executed by the processor does a digital device seem to carry out any useful actions.
◗Are you talking about a computer program? Not exactly. Let’s use a game like Fruit Ninja as an example. This game is written by programmers using a programming language such as C++, BASIC, COBOL, or Java. When we think of a computer program, we think of the long list of statements written in one of these programming languages. Surprisingly, microprocessors can’t directly understand these programming languages, so programs like Fruit Ninja have to be converted into machine language that corresponds to the microprocessor’s instruction set. These machine language instructions are binary strings of 0s and 1s that can be processed by a digital device.
◗What are machine language instructions like? Machine language instructions are like baby steps. Take a look at the commonly used machine language instructions in Figure 2-25. It seems incredible that digital devices can carry out such a wide variety of tasks using such limited instructions.
QUICKCHECK
An instruction set is _________.
a.a set of commands, such as Print and Get, that programmers use to create software
b.the collection of preprogrammed activities that a microprocessor can perform
c.a command that is in binary format d.the options that appear on a software application’s main menu

◗What happens inside a computer chip? A microprocessor contains miles of microscopic circuitry and millions of miniature components divided into different kinds of operational units, such as the ALU and the control unit. The ALu (arithmetic logic unit) is the part of the microprocessor that performs arithmetic operations, such as addition and subtraction. It also performs logical operations, such as comparing two numbers to see if they are the same. The ALU uses registers to hold data that is being processed. As an analogy, registers are similar to a mixing bowl you might use to hold the ingredients for a batch of cookies. The microprocessor’s control unit fetches each instruction, in the same way you might get ingredients for cookies out of a cupboard or the refrigerator. Data is loaded into the ALU’s registers, just like you add all the cookie ingredients to the mixing bowl. Finally, the control unit gives the ALU the green light to begin processing, just the way you flip the switch on your electric mixer to blend the cookie ingredients. Figure 2-26 illustrates a microprocessor control unit and its ALU preparing to add 5 + 4.
QUICKCHECK When the control unit swings into action, which step comes first?

P erform arithmetic operations.
Load data into the ALU.
Fetch an instruction.
Execute the instruction.

◗What happens when a computer executes an instruction? The term instruction cycle refers to the process in which a computer executes a single instruction. Some parts of the instruction cycle are performed by the microprocessor’s control unit; other parts of the cycle are performed by the ALU. The steps in this cycle are summarized in Figure 2-27.
QUICKCHECK
Of course, the processor in Figure 2-26 would be using binary for the instruction and data. What is the binary machine language instruction for ADD? (Hint: Look back at Figure 2-25.)

0000 0000
0101 0100
1110 1110
1111 1111

◗What role does the control unit play? The machine language instructions for a particular program are held in memory. When the program begins, the memory address of the first instruction is placed in a part of the microprocessor's control unit called an instruction pointer.
Figure 2-28 shows how the control unit can then go to the memory address (A) and fetch the instruction by copying data from that address into its instruction register (B). Next, the control unit interprets the instruction and executes it (C).

◗When does the ALU swing into action? The ALU is responsible for performing arithmetic and logical operations. As shown in Figure 2-29, the ALU uses registers to hold data that is ready to be processed. When it gets the go-ahead signal from the control unit (A), the ALU processes the date and places the result in an accumulator (B). From the accumulator, the date can be sent to memory or used for further processing. When the com- puter completes an instruction, the control unit increments the instruction pointer to the memory address of the next instruction, and the instruction cycle begins again.

PERFORMANCE
Now that you have some background on how microprocessors work, you can begin to appreciate what makes some microprocessors perform better than others. A microprocessor’s performance is affected by several factors, including clock speed, number of cores, processing techniques, cache size, word size, and instruction set.
◗What does GHz have to do with processor performance? A processor specification, such as 3.4 GHz, indicates the speed of the
microprocessor clock—a timing device that sets the pace for executing instructions. Most computer ads specify the speed of a microprocessor in gigahertz. Gigahertz (GHz) means a billion cycles per second. A specification such as 2.13 GHz means that the microprocessor’s clock operates at a speed of 2.13 billion cycles per second. A cycle is the smallest unit of time in a microprocessor’s universe. Every action a processor performs is measured by these cycles. It is customary to equate clock cycles with the number of instructions a processor can execute per second. There is not always a one-to-one correspondence, however. Some instructions are processed within one clock cycle, but other instructions might require multiple cycles. Some processors can even execute several instructions in a single clock cycle. You might expect a computer with a 2.13 GHz processor to perform slower than a computer with a 3.4 GHz processor. This is not necessarily the case. Clock speed comparisons are only valid when comparing processors within the same chip family. A 2.13 GHz processor could outperform a 3.4 GHz processor. Why? Because factors other than clock speed contribute to the overall performance of a microprocessor.
◗What’s a multi-core processor? The “core” of a microprocessor consists of the control unit and ALU. A microprocessor that contains circuitry for more than one processing unit is called a multi-core processor. Having more cores usually equates to faster performance. The 2.4 GHz Intel i5 processor has two cores, giving it the equivalent of 4.8 GHz performance (2.4 x 2). The 1.6 GHz Intel i7 processor has four cores, giving it the equivalent of 6.4 GHz performance (1.6 x 4). Figure 2-30 illustrates a microscopic view of a processor with multiple cores.

QUICKCHECK
Which one of the following statements is true?

A microprocessor executes one instruction for each clock cycle.
A 2.4 GHz Intel i5 processor is faster than a 1.6 GHz Intel i7 processor.
Clock speed is the most important factor that affects processor performance.
A multi-core processor can outperform a single-core processor that has a faster clock speed.
Terminology

The thin wafer of silicon and the microscopic circuitry it contains is called a die. Figure 2-30 illustrates a microprocessor die with four cores.
Can a microprocessor execute more than one instruction at a time? Some processors execute instructions "serially"—that is, one instruction at a time. With serial processing, the processor must complete all steps in the instruction cycle before it begins to execute the next instruction. To use an analogy, visualize a pizzeria with one small oven. The pizzas are instructions; the oven is the microprocessor. Pizzas (instructions) are processed one at a time.
Now, what if the pizzeria rigs up a conveyor-belt through the oven. A pizza (instruction) starts moving along the conveyor belt into the oven; but before it reaches the end, another pizza starts moving along the belt. When a pro- cessor begins to execute an instruction before it completes the previous instruction, it is using pipeline processing.
A pizzeria might also have large ovens that hold multiple pizzas. Just as these ovens can bake more than one pizza at a time, parallel process- ing executes more than one instruction at a time. This eﬃcient processing technology is possible with today's multi-core microprocessors. Pipeline and parallel processing oﬀer better performance than serial pro- cessing (Figure 2-31 ).

QUICKCHECK
Many of today's digital devices are capable of parallel processing because:

Their processors have multiple cores.
They have pipelining.
They can run more than one program at a time.
They have high GHz specifications.

◗How does cache size affect performance? CPU cache (pronounced "cash") is special high-speed memory that allows a micropro- cessor to access data more rapidly than from memory located elsewhere on the system board. A large cache can increase processing performance.
CPU cache is structured into several levels. Level 1 cache (L1) is the fast- est, whereas Level 2 (L2) and Level 3 (L3) are slightly slower but still faster than accessing main memory or disk storage. Cache capacity is usually measured in megabytes.
◗What impact does word size have on performance? Word size refers to the number of bits that a microprocessor can manipulate at one time. it corresponds to the size of the registers used by the control unit and ALU. A processor with a 64-bit word size, for example, has regis- ters that can process 64 bits at a time.
Word size controls the amount of memory that the processor can access. Processors with a 32-bit word size can access a maximum of 4 GB of memory, whereas processors with a 64-bit word size can potentially access many terabytes of memory.
A large word size gives processors the ability to handle more data dur- ing each processing cycle—a factor that leads to increased performance. Today's digital devices typically contain 32-bit processors or 64-bit pro- cessors. in a computer with a 32-bit word size, registers that hold data and those that hold instructions all have capacity for 32 bits (Figure 2-32).
TRY lT!
Take another look at the processor specifications for your favorite desktop or laptop computer. Can you tell if its processor has a 32-bit or 64-bit word size?

◗How does an instruction set affect performance? As chip designers developed various instruction sets for microprocessors, they added increasingly complex instructions, each requiring several clock cycles for execution. A microprocessor with such an instruction set uses ClSC (complex instruction set computer) technology. A microprocessor with a limited set of simple instructions uses RlSC (reduced instruction set com- puter) technology.
A RlSC processor performs most instructions faster than a ClSC processor. it might, however, require more of these simple instructions to complete a task than a ClSC processor requires for the same task.
Most processors in today's desktop and laptop computers use ClSC tech- nology. Many processors in handheld devices, such as smartphones and tablets, use ARM (Advanced RlSC Machine) technology.
QUlCKCHECK
x86 processors use

RlSC technology
ClSC technologv
ARM technology
RANDOM ACCESS MEMORY RAM (random access memory) is a temporary holding area for data, application program instructions, and the operating system. RAM can be packaged in a chip carrier that is wired to the system board or it can be located on small circuit boards that plug into the system board.

◗How much RAM does a device need? When purchasing a digital device, you may have a choice of RAM capacity. Higher RAM capacity adds to the expense of a device. RAM capacity is expressed in gigabytes. Today’s desktop and laptop computers typically feature 2–8 GB of RAM. Handheld devices usually have 1–3 GB of RAM.
◗But my smartphone has 64 GB, right? Your smartphone has RAM, but not 64 GB. The specifications for smartphones that describe “memory” capacity are not referring to RAM, but to another kind of storage that is more permanent. You’ll learn more about this type of storage in the next section. For now, let’s focus on RAM and why it is such an essential component of your favorite digital devices.
◗Why is RAM so important? RAM is the “waiting room” for the microprocessor. It holds raw data waiting to be processed as well as the
program instructions for processing that data. RAM also holds the results of processing until they can be moved to a more permanent location such as an internal drive, flash drive, or cloud storage. In addition to data and application software instructions, RAM also holds operating system instructions that control the basic functions of a computer system. These instructions are loaded into RAM every time you turn on a digital device, and they remain there until you turn off the device (Figure 2-33).
Try iT!
Find out how much RAM is in your favorite digital device. If you’re working with a laptop or desktop, you can access RAM specs the same way you found the processor specifications.

◗How does RAM work? In RAM, microscopic electronic parts called capacitors hold the bits that represent data. You can visualize the capacitors as microscopic lights that can be turned on or off. A charged capacitor is “turned on” and represents a “1” bit. A discharged capacitor is “turned off” and represents a “0” bit. A RAM address on each bank helps the computer locate data, as needed, for processing. Unlike disk storage, most RAM is volatile, which means it requires electrical power to hold data. If the device is turned off, if the battery runs out of juice, or if a desktop computer is accidentally unplugged or experiences a power failure, all data stored in RAM instantly and permanently disappears. This type of RAM is technically classified as dynamic RAM (DRAM), but it is commonly referred to simply as RAM.
QUICkCHECk
The programs and data in RAM disappear when ___________.

the device goes to sleep
the device is turned off
you close a program
all of the above
◗Can a device run out of memory? Suppose that you want to work with several programs and large graphics at the same time. Will your device eventually run out of memory? The answer is probably not. if a program exceeds its allocated space, the Operating system uses an area of the hard disk or other storage medium as virtual memory to store parts of programs or data files until they are needed.

By selectively exchanging the data in RAM with the data in virtual mem- ory, your computer eﬀectively gains almost unlimited memory capacity. Too much dependence on virtual memory can decrease performance, however, especially if virtual memory is located on a relatively slow mechanical device, such as a hard disk drive.
READ-ONLY MEMORY
ROM (read-only memory) is a type of memory circuitry that is housed in a single integrated circuit on the system board. Whereas RAM is tempo- rary and volatile, ROM is more permanent and non-volatile. The contents of ROM remain in place even when the device is turned off.
◗Why do digital devices have ROM? When you switch on a digi- tal device, there is a waiting period while the device gets ready for use. While you are waiting, ROM is performing its role to "boot" the device. The boot process varies from one kind of device to another; but in gen- eral, it begins when you press the power button and ends when the device is ready to use.
ROM contains a small set of instructions and data called the boot loader. The boot loader instructions tell a digital device how to start. Typically, the boot loader performs seIf-tests to find out if the hardware is Operating properly and may also verify that essential programs have not been cor- rupted. it then loads the Operating system into RAM.
◗Why isn't the boot loader stored in RAM? RAM requires power to hold data. When a device is oﬀ, RAM is empty. When you turn on the device, RAM is still empty and doesn't contain any instructions for the microprocessor to execute. ROM, on the other hand, holds data even when the power is oﬀ. As Figure 2-34 shows, when you press the power button (A), your device can immediately access the instructions in ROM and proceed with the startup routine (B). Only when the startup is com- plete can you access apps and data (C).

Terminology A ROM chip, along with its instructions, is commonly referred to as firmware because it is a combination of hardware and software.
QUlCKCHECK
While you are waiting for a digital device to boot, all of the following occur except:

The microprocessor fetches data from the ALU.
The boot loader checks hardware functions.
instructions in ROM verify that essential programs have not been corrupted.
The Operating system is loaded into RAM.
◗Can I change the contents of ROM? The process of changing the contents of ROM is sometimes called "flashing" because it is similar to the way a camera flash helps the camera capture an image. There are sev- eral reasons that you might want to change the contents of ROM and boot loader instructions.

RepairElectrical surges and other hardware problems might corrupt the contents of ROM, which would prevent the device from powering on prop- erly. Flashing the ROM to restore the boot loader instructions might correct the problem.
User modificationThe boot loader may limit the programs that can be downloaded and run on a device. Flashing the ROM with a modified boot loader can bypass these limitations. The process is sometimes called "jail- breaking" on iOS devices and "rooting" on Android devices. These ROM modifications may cause more problems than they solve and may void the device's warranty.
Forensics Tricky criminals may hide incriminating data in ROM, or they may alter the boot loader so that it deletes incriminating files when the device is powered on by an unauthorized person. lnvestigators may want to examine the BlOS for hidden data, and they may have to flash the BlOS to restore it to a non-destructive state.
Updates. Device manufacturers oﬀer updates to the boot loader as neces- sary to patch security weaknesses. Such updates are performed by running a program supplied by the manufacturer. Be sure to back up your device before flashing, and carefully follow instructions for this procedure. if the flesh fails, your device will not start until you get the ROM chip replaced. After a successful update (Figure 2-35), your device should boot normally.

Terminology There are many types of non- volatile memory, such as EEPROM and NAND, but for convenience the term ROM is used for all of them. Technically, the contents of ROM cannot be changed. The EEPROM and NAND chips that hold the boot loader programs for modern computers can be changed by flashing.
TRY lT!What does Apple have to say about jailbreaking iPhones and iPads? You can find out by conducting an online search for support apple jai/break.

sectionD

STORAG

STORAGE BASlCS
Storage is the term used for the components of a digital device designed to hold data permanently. Unlike RAM, storage is non-volatile and retains data even when the device is powered down. Storage is used to save doc- uments, photos, and playlists. lt also houses software and the operating system.
Today's digital devices may use local storage and remote storage, but they are not interchangeable. To find out what gets stored where, let's look at local storage first, then expand into remote storage.
◗Which local storage technology is best?
Local storage refers to storage devices and media that can be directly attached to a computer, smartphone, or appliance. Local storage options include hard drives, CDs, DVDs, flash drives, solid state drives, and memory cards.
Most digital devices have some type of local storage that is permanently available as you use the device. Built-in storage can be supplemented by removable storage, such as flash drives and memory cards.
Each of these local storage options has its advantages and disadvantages. lf one storage system were perfect, we wouldn't need so many storage devices connected to our digital devices! To compare local storage options, it is useful to review their durability, dependability, speed, capacity, and cost (Figure 2-36).

◗How much storage do I have?
The amount of local storage avail- able on a digital devices depends on the capacity of each storage device and the amount of data that is currently stored. Available storage space is sometimes referred to as "free space." The process of finding the amount of free space depends on the device. Figure 2-37 can get you started.

◗How do storage technologies work? You can think of your computer's storage devices as having a direct pipeline to RAM. Data gets copied from a storage device into RAM, where it waits to be processed. After data is processed, it is held temporarily in RAM, but it is usually copied to a storage medium for more permanent safekeeping.
As you know, a computer's processor works with data that has been coded into bits that can be represented by 1s and Os. When data is stored, these 1s and Os must be converted into some kind of signal or mark that's fairly permanent but can be changed when necessary.
Obviously, the data is not literally written as "1" or "."0 lnstead, the 15 and Os must be transformed into something that can remain on a storage medium. Exactly how this transformation happens depends on the storage technol- ogy. For example, hard disks store data in a different way than CDs. Three types of storage technologies are commonly used for personal computers: magnetic, optical, and solid state.
Terminology
The process of storing data is often referred to as writing data or saving afi/e because the storage device writes the data on the storage medium to save it for later use.
The process of retrieving data is often referred to as reading data, loading data, or opening a file.
MAgneTiC STOrAge TeChnOlOgy
Those big reels of tape that you see on computers in classic science fiction movies are an example of magnetic storage technology used on data processing era mainframe computers. The first personal computers used cassette tapes for storage, though floppy disk storage was soon available. Today, magnetic storage technology is the foundation for the hard disk drives in desktop computers, laptops, and enterprise servers.
◗What is magnetic storage technology?
Magnetic storage represents data by magnetizing microscopic particles on a disk or tape surface. The particles retain their magnetic orientation until that orientation is changed, providing permanent but modifiable storage for data. Data stored magnetically can be easily changed or deleted simply by changing the magnetic orientation of particles on the disk surface. This feature of magnetic storage provides lots of flexibility for editing data and reusing areas of a storage medium containing unneeded data.
◗How does a hard disk drive work?
A hard disk drive contains one or more platters and their associated read-write heads. A hard disk platter is a flat, rigid disk made of aluminum or glass and coated with magnetic iron oxide particles. The platters rotate as a unit on a spindle, making thousands of rotations per minute. Each platter has a read-write head that hovers just a few microinches above the surface. A read-write head mechanism in the disk drive magnetizes particles to write data, and senses the particles’ polarities to read data (Figure 2-38).

Terminology
You might hear the term fixed disk used to refer to hard disks. You often see the terms hard disk and hard disk drive used interchangeably, though technically hard disk refers to the platters sealed inside the hard disk drive.
◗What are the advantages of hard disk drives?
Hard disk drives can be installed inside a device or attached externally for additional storage capacity or backup. Hard disk technology has three advantages. First, it provides lots of storage, with capacities ranging from 40 GB to 8 TB. Second, it provides fast access to files. Third, hard disk drives are economical. The cost of storing 1 gigabyte of data is about two cents.
QUICKChECK
What is the purpose of a readwrite head?

It pulls particles up as data is read.
It etches a track on the disk surface.
It orients particles north or south depending on if they represent 0s or 1s.
◗What’s the downside of hard disk storage?Data stored on magnetic media can be unintentionally altered by magnetic fields, dust, mold, smoke particles, heat, and mechanical problems with a storage device. Over time, magnetic media gradually lose their magnetic charge. Some experts estimate that the reliable lifespan of data stored on magnetic media is about three years. They recommend that you refresh your data every two years by recopying it. The read-write heads in a hard disk drive hover a microscopic distance above each platter. If a read-write head comes into contact with the platter, the head crash is likely to damage the platter and corrupt the data contained on it. The causes of a head crash are explained in Figure 2-39.

◗What should I know about hard disk drive specifications?
Computer ads commonly specify the capacity, access time, and speed of a hard disk drive. For example, “2 TB 8 ms 7200 RPM HDD” means a hard disk drive with a 2 terabyte capacity, an access time of 8 milliseconds, and a speed of 7,200 revolutions per minute. Access time is the average time it takes a computer to locate data on the storage medium and read it. Hard disk access times of 6 to 11 ms are not uncommon. Hard disk drives have much faster access times than CDs, which take about 500 ms to spin up to speed and find data. Hard disk drive speed is sometimes measured in revolutions per minute (rpm). The faster a drive spins, the more rapidly it can position the readwrite head over specific data. For example, a 7,200 rpm drive is able to access data faster than a 5,400 rpm drive. When comparing hard disk drives to other storage technologies, data transfer rates can be useful. Data transfer rate is the amount of data a storage device can move per second from the storage medium to RAM. Higher numbers indicate faster transfer rates. The average data transfer rate for a hard disk drive is about 57,000 KBps (also expressed as 57 MBps or MB/s).
QUICKCHECK
If you see an ad for a computer with a 6 ms hard drive, you can assume that 6 ms refers to the drive’s ___________. a. access time

capacity
rotational speed
data transfer rate
Try iT!

Check online. What’s the average price for a 2 TB hard drive?
OPTlCAL STORAGE TECHNOLOGY
Devices that store data on CDs, DVDs, and Blu-ray discs may seem out- dated, yet optical technologies remain useful for archival storage because they can provide a permanent home for collections of documents, music, and photos that you might not trust to less robust storage technologies.

◗How does optical technology work?
CD, DVD, and Blu-ray (BD) technologies are classified as optical storage, which represents data as microscopic light and dark spots on the disc surface. An optical drive con- tains a laser that directs a beam of light toward the underside of the disc. Reflected light is collected by a lens and converted into Os and 1s that rep- resent data.
◗How do CD, DVD, and Blu-ray technologies differ?
A single optical drive typically handles CDs, DVDs, and Blu-ray discs, but the costs and capacities of these discs vary (Figure 2-40).

◗What's the significance of ROM, R, and RW? Optical technolo- gies are grouped into three categories:
Read-only (ROM). CD-ROMS and DVD-ROMS are mass produced. Their contents cannot be changed; their lifespan is estimated to be 100 years.
Recordable (R). Data can be written on a recordable disc by consumer devices, but once written, the data cannot be changed. Lifespan: 100 years.
Rewritable (RW). Data can be written on the disc and later changed. The estimated lifespan of data is about 30 years.
◗How durable are optical discs? Optical discs are not disrupted by humidity, fingerprints, dust, magnets, or spilled soft drinks. Some optical discs have an estimated lifespan of at least 30 years, while other types of optical discs can probably hold data securely for up to 100 years. When using optical technology for archival purposes, the archive should include an optical drive as well as the media containing data. The drive that recorded the data will have the best chance of reading it as the years go by.
near infrared laser.
Terminology Writing data on a CD, DVD, or BD is often called burning because the laser essentially burns a pit in the disc.
QUlCKCHECK
Which optical technology performs most similarly to a hard disk drive?

SOLlD STATE STORAGE TECHNOLOGY
lf you're a typical digital device owner, you use solid state storage every day. You carry a flash drive and you might swap memory cards in a camera or tablet. The main storage for your smartphone is also based on solid state technology, as is the storage for many of today's Iaptops.
◗What is solid state storage? Solid state storage (sometimes called flash memory) stores data in erasable, rewritable circuitry, rather than on spinning disks or streaming tape. Each data bit is held in a gate-like circuit that can be open or shut.
Very little power is required to open or close the gates, which makes solid state storage ideal for battery-operated devices, such as digital cameras and media players. Once the data is stored, it is non-volatile—the circuits retain data without the need for an external power source.
Solid state storage provides fast access to data because it includes no moving parts. This storage technology is very durable—it is virtually imper- vious to vibration, magnetic fields, or extreme temperature fluctuations. it is also dependable. With no mechanical parts, it is less likely to fail than a hard disk drive.
◗When should I use memory cards?
A memory card is a flat, solid state storage medium commonly used to transfer files from digital cameras and media players to computers. The term memory card might lead you to believe that it is similar to random access memory (RAM). However, these cards are non-volatile, so they retain data even when they are disconnected from computers and other devices.
QUlCKCHECK
The formats for memory cards include CompactFlash, MultiMediaCard, Secure Digital (SD), and SmartMedia. A card reader is a device that reads and writes data on solid state storage. Sometimes referred to as 5-in-1, 7-in-1, or all-in-one card readers, these combination devices work with mul- tiple types of memory cards (Figure 2-41 ).

QUlCKCHECK in what way are memory cards and RAM similar?

They are volatile.
They are non-volatile.
They are for temporary storage.
. They are solid state.
TRY lT! Check the device you are currently using. Does it have a built—in card reader?
Card reader
Memory cards are available in Many digital devices are equipped with a card reader for several formats and capacities. transferring data to and from solid state memory cards.
DlGlTAL DEVlCES
◗Do I need a solid state drive?Asolid state drive (SSD) is a pack- age of flash memory that can be used as a substitute for a hard disk drive. An SSD is installed inside the system unit and is not meant to be removed except for servicing. Some solid state drives are about the same size as a microprocessor chip; others are about the size of a small deck of cards (Figure 2—42).

◗What should I know about USB flash drives?A USB flash drive is a portable storage device that plugs directly into a computer's system unit using a built-in USB connector. Also called thumb drives, pen drives, jump drives, keychain drives, or UFDs, USB flash drives are about the size of a highlighter pen and so durable that you can literally carry them on your key ring. USB flash drives have capacities ranging from 16 MB to 1 TB.
The data transfer rate of a USB flash drive depends on the USB version. USB 1.0 is quite slow. USB 2.0 can read data at a rate of 800 Mbps, whereas USB 3.0 rates can reach 5 Gbps, rivaling hard disk drive speed.
CLOUD STORAGE
You probably use several digital devices. Suppose you stored class notes on your laptop, but you've left it at home. imagine if you could access those notes from your phone. Cloud storage can make that happen.

◗What is cloud storage?
Storage that is built into a digital device or that can be plugged directly into a device is classified as local storage. ln contrast, remote storage is housed on an external device that can be accessed from a network. Remote storage may be available on a home, school, or work network. it can also be available as an lnternet service, in which case it is called cloud storage.
Cloud storage is provided to individuals by services such as Apple iCloud, Microsoft OneDrive, Google Drive, and Dropbox. The basic concept is that files can be stored in a subscriber's cloud-based storage area and accessed by logging in from any device. in a simple implementation, cloud storage functions just like a local drive (Figure 2-43).

QUlCKCHECK Which of the following is a good substitute for a hard disk drive?

An SSD
A memory card
A USB flash drive
A DVD—RW
Some cloud implementations offer a synchronization feature that automati- cally duplicates files stored on a local device by also saving them in the cloud (Figure 2-44).

◗What should l know about cloud storage? The term cloud storage refers to a set of technologies for transporting, synchronizing, and managing data stored on banks of high-performance hard disk drives housed in the service provider's data center.
Most cloud services offer a generous amount of free storage space, so the price is right. if you regularly use several digital devices and want to access your files from all of them, then cloud storage is an excellent solution. Also, if you procrastinate about backing up your devices, files stored in the cloud remain there even if a local device malfunctions. That being said, cloud storage has several drawbacks.
Security and privacy risks. The more places your data is stored and the more networks on which it travels, the more susceptible it becomes to inter- cepts from hackers and spying agencies. Carefully consider what you store in the cloud.
Service outages. When a cloud storage site has an outage, all the data stored there becomes temporarily inaccessible. if you have a term paper due in two days, it would be best not to trust the only copy to cloud storage where a two-day outage could make your files inaccessible until after the due date.
Discontinuation of service. Some cloud storage providers have shuttered their storage services with little warning to customers. Cloud storage may offer a convenient option for backing up your files, but don't depend on it as the only backup.
SECTlON D, MODULE 2
QUlCKCHECK Cloud services generally use what type of storage devices?

Magnetic
Optical
Flash
Cloud circuits
DlGlTAL DEVlCES

BACKUP
Storage devices fail. Cloud storage services go dark. When they do, the date they contain might not be recoverable. To protect your data, you need backups. Do you have them? Do they contain the files you'll need to resume work without a hitch?
◗ What do I really need to back up? A backup is a copy of one or more files that is made in case the originals become damaged. Although the best practice might seem to be "back up everything," that is not always practical.
Your files are often scattered—some on a local hard disk, others on USB drives, some on your phone, and even others on cloud storage. Simply copying all of your files from one device to another or to the cloud requires lots of space and lots of time. Plus, there are some sticky technical issues that make it diﬃcult to actually get a complete backup. To understand the problem, consider what a typical hard disk contains (Figure 2-45).

◗Then What should I do? The best advice is this: Know what's impor- tant and ensure that current versions exist on more than one storage device. The easiest pairings of devices for backups are illustrated in Figure 2-46.

TRY IT! How many GB Of data would be stored in a backup of the entire contents of your desktop or laptop computer? (Hint: Figure 2-37 showed you how to check the amount of space that is used on a local hard disk.)
(
Back up hard Back up hard disk Back up handheld Back up handheld Back up cloud disk to cloud to external drive to hard disk to cloud to hard disk

◗What tools do I need for backups? The tools you'll need depend on what you are backing up and where you are putting the backups. if you are a typical consumer with a laptop and a smartphone, you will need a cloud storage account, an external hard disk drive, synchronization soft- ware, a blank USB flash drive, and backup or disk imaging software. I l've got a Windows PC. What should ! do? Windows users have access to several backup tools and will need to use more than one of them.
Recovery drive. A recovery drive (or system repair disc) contains parts of the operating system necessary to boot your computer and diagnose system problems after a hard drive failure or software malfunction. Files for creating a recovery drive are usually preinstalled on the hard disk drive, but they won't do you any good there when the hard disk fails. Follow the manufacturer's instructions to move the recovery files to a blank USB flash drive, which you can store until it is needed.
Copy command. As you are working on important projects, make cop- ies of essential files. You can store the copies on the same device as the originals using versioning techniques, such as adding "v2" and "v3" to the fiIe names of versions. And for safety, periodically copy a version to a USB drive or to cloud storage. You can manually create copies of your data files using the Copy option in Windows File Explorer.
File History. Data file backup can be automated using File History, which is included with Windows 8.0 and subsequent versions. File History uses file synchronization to make copies of files from your Documents, Music, Pictures, and Videos folders, along with any files that were created or mod- ified while OneDrive was oﬄine. File History is useful if a data file goes missing, but it requires the System lmage Backup option for system files, software, and settings. File History is easy to set up (Figure 2-47).

QUlCKCHECK Which backup tool can be used to boot a Windows computer after a hard drive malfunction?

A recovery drive
The Copy command
File History
A cloud drive

System image. A disk image is a bit-for-bit copy of the data from all sec- tors of a hard disk. Windows includes a disk imaging option called System lmage that creates an exact clone of the original disk, including the oper- ating system, your software, and all your settings. Be sure to select the System lmage Backup option in the File History window to activate it. I if my computer's hard drive fails, how do ! proceed? First, a new hard drive has to be installed. Then, as shown in Figure 2-48, (A) use the recovery drive to boot the computer. Then, (B) attach the backup drive containing your system image. Respond to the prompts displayed on the screen to copy the system image to the new hard disk. After the system image is installed, recover your files by using the File History utility.

I have a Mac.
◗What's my best backup option? MacOS oﬀers a comprehensive file synchronization utility called Time Machine, which backs up the entire hard disk, including system files, applications, accounts, preferences, email messages, music, photos, movies, and docu- ments. Make sure that Time Machine is set to run in the background at all times while your computer is turned on.
Backup drive
if you need to restore a single file, you can open Time Machine, choose a file, and then select the Restore option. To restore an entire backup, make sure the backup drive is connected and hold down the Command and R keys as the computer starts. Figure 2-49 illustrates the Time Machine.
You can select a day or time to view files as they existed on that date.

QUlCKCHECK ln Figure 2—48, what is stored on the USB flash drive?

All the files that the user has backed up
Parts of the operating system needed to boot the computer
A system image
A synchronized backup

◗What about backing up my smartphone and tablet? Many Android devices include backup software, which is usually accessible from the Settings icon. Generally, backups from Android devices are stored in the cloud on Google servers. lf your Android device accepts SD cards, you may also be able to make backups of individual files.
Owners of iOS devices can back up to a local computer using iTunes or to iCloud. The process is usually referred to as synchronization because it updates the files on the backup device with newer versions of files found on the smartphone or tablet.
To activate iCloud backup, you can access Settings for your iOS device, tap iCloud, and then select Backup. Slide the iCloud Backup button to On. To sync to a local drive using iTunes, simply connect the device to a desktop or laptop using a USB cable. Make sure iTunes is open. Choose File, select
SECTlON D, MODULE 2
Devices, and then select Backup (Figure 2-50).

EXPANSION PORTS Like an ocean liner’s portholes, many digital devices have ports in the system unit for connecting cables and various add-ons. Because these ports expand the options for input, output, and storage, they are commonly called expansion ports. When you plug in a USB flash drive or insert a memory card, you are using an expansion port. ◗ How do expansion ports relate to the rest of the circuitry in a device?
All of the components on the system board are connected by circuitry. The main circuits that carry data are called the data bus. These circuits carry data at lightning speeds as pulses of electrical voltages. The part of the data bus that runs between the microprocessor and RAM is called the local bus or internal bus. This is the fastest part of the data bus because it has to keep up with the data demands of the microprocessor. The part of the data bus that stretches from RAM to various expansion ports is called the expansion bus. This part of the bus has several branches to accommodate data traveling to and from various ports (Figure 2-52).

◗**What should I know about expansion ports? When making a connection between a peripheral device and a computer, the cable must connect to the proper expansion port. Ports are sometimes marked by tiny symbols that are diﬃcult to see. You'll want to be able to identify ports by their size and shape.
From Section D, you are already familiar with the storage ports used for memory cards. You'll also want to be able to identify general-purpose, video, audio, and network ports (Figure 2—53).

TRY lT! Take a look at your laptop or desktop computer. Can you make a list of all its ports?

Terminology An adapter converts one type of connector to another. For example, a projector might have a DVl connector; but if your Iaptop has only a Mini DisplavPort, you can use an adapter to change the DVl plug to a Mini DisplayPort plug.

QUlCKCHECK Which port would be the first choice for connecting a display device?

DVI
USB
Thunderbolt
Ethernet

◗**What is hot-plugging? When a peripheral device is connected or disconnected while the host device is operating, it is called hot-plugging. Although it is unnecessary to turn devices off before disconnecting them, some devices should not be disconnected while in the middle of data trans- fers. Before unplugging a device, such as a USB flash drive, your computer might require notification. Figure 2-54 shows how to safely remove a USB drive.

◗**What if ! run out of USB ports? if you want to connect more devices than the available number of USB ports, you can use a USB hub. A USB hub is an inexpensive device that turns one USB port into multi- ple ports. lt also saves wear and tear on USB ports caused by repeatedly inserting and removing USB devices (Figure 2-55).

QUlCKCHECK When you're ready to put your laptop in your backpack, which of the following do you need to eject?

A printer that's connected with a USB cable
A USB flash drive
The mouse
All of the above
Do you have any devices connected to your computer that require notification before they are removed? (Hint: Use one of the methods in Figure 2-54 to find out.)

BLUETOOTH
lncreasingly, gadgets are going wireless. lnstead of exchanging data through a cable, devices can send signals through the air—no cable required. A common wireless technology for connecting peripherals is Bluetooth.
◗What kinds of devices use Bluetooth?
You'll find Bluetooth options for connecting wireless keyboards and mice to laptops and desk- tops. Nintendo and Wii game controllers also use Bluetooth.
Bluetooth is a low-power technology, so it is ideal for mobile devices that don't have big batteries. Bluetooth is used to connect wireless headsets to smartphones. And if you're into fitness, then your armband or smartshoes may transmit data to your phone or computer using Bluetooth technology.
◗What are the range and speed of Bluetooth? Bluetooth devices must be within 30 feet of each other. The peak data transmission rate is 3 Mbps, which is suitable for sending small bursts of data rather than large files. Compared to wired connections, Bluetooth is quite slow (Figure 2-56).

◗Can I tell if a device is equipped with Bluetooth?
Bluetooth is built into many smartphones, tablets, laptops, and desktops, but there is no corresponding physical port on the system unit. Look for the Bluetooth logo on the Windows taskbar or the Mac menu bar (Figure 2-57). For handheld devices, check Settings. if a device is not equipped with Bluetooth, you can plug a Bluetooth antenna into a USB port

QUlCKCHECK Which of the following would be least likely to connect through a Bluetooth port?

A wireless headset
An external hard drive
A keyboard
A game controller
TRY lT! Does your favorite device have Bluetooth? Look for the Bluetooth icon or settings to find out.

© 2015 Hewlett-Packard Development Company, L.P.
DlGlTAL DEVlCES
DEVlCE DRlVERS
Many gadgets have associated software. For example, there's an iPhone app for your fitness wristband that graphs your progress and shares it with your training buddies. These applications help you get the most out of your gadgets. ln addition to application software, devices also require a type of software called a device driver. ◗What's a device driver? A device driver is software that helps a peripheral device establish communication with its host device. For exam- ple, the device driver for an HP printer sets up data streams from RAM to the printer and makes sure that the date is formatted in a way that the printer can work with. ◗When do I have to install device drivers? Operating systems include built-in drivers for standard expansion ports. This feature, some- times called Plug and Play, makes it easy to connect devices without manually installing device drivers. When you connect a new peripheral device, the operating system looks for an appropriate driver. lf the device is unable to use a standard driver, you'll be prompted to install the device driver supplied by the peripheral device manufacturer. ◗Where do I get device drivers? Device drivers, updates, and instructions for installing them can also be downloaded from the manufac- turer's Web site.
◗When do I need a device driver update? Device drivers work directly with the host device's operating system. A printer or other con- nected gadgets might work perfectly—until the operating system gets an update. Then some device drivers might stop working correctly and the devices they control could malfunction.
ln addition to checking cables, trying a different port, and rebooting, one of the first steps in troubleshooting a malfunctioning peripheral device is to access the manufacturer's Web site and look for a driver update. Updated driver downloads are usually available from the Support link (Figure 2-58).

QUlCKCHECK
Suppose you just got an operating system update and now your printer has stopped working. What can you do to solve the problem?

Go online and check for a printer driver update.
Connect the printer using a different port.
Reboot the computer.
All of the above.
SECTlON E, MODULE 2

DlSPLAY DEVlCES
A computer display device that simply displays text and images is clas- sified as an output device. Touchscreens, however, can be classified as both input and output devices because they accept input and also display output.
◗What are my options for display devices? Standalone display devices, sometimes called monitors, are popular for desktop computers. Display devices for laptops, tablets, and handheld devices are built into the system units, but these devices may also accept an external monitor. Two technologies are commonly used for display devices: LCD and LED.
LCD (liquid crystal display) technology produces an image by filtering light through a layer of liquid crystal cells (Figure 2-59). The advantages of LCD screens include display clarity, Iow radiation emission, portability, and com- pactness. The source of the light that filters through the LCD is referred to as backlighting. Most modern screens are backlit with LED (light-emitting diode) technology and are marketed as LED displays.

QUlCKCHECK The liquid crystal cells used in display devices do not directly emit light, so is necessary. Each dot, or pixel, on the screen contains three liq- uid crystal cells: one red, one green, and one blue. / Andrey Burmakin/Shutterstockcom a. backlighting b. conversion / c. RGB

battery backup
Controlling the levels of red, green, and blue produces various colors; in this case, orange. Liquid crystal cells produce no light on their own, so backlighting is used for illumination.

◗What factors affect image quality? lmage quality is a factor of screen size, response rate, dot pitch, and screen resolution.
Screen size. Screen size is the measurement in inches from one corner of the screen diagonally across to the opposite corner. Screen sizes range from 1" for smartwatches to 60" or more for home entertainment systems.
Response rate. Response rate is the time it takes for one pixel to change from black to white then back to black. Display devices with fast response rates display a crisp image with minimal blurring or "ghosting" of moving Objects. Response rate is measured in milliseconds (ms). For gaming sys- tems, a response rate of 5 ms or less is desirable.
Dot pitch. The LEDs that form an image on the screen are spaced in a grid. Dot pitch (dp) is the distance in millimeters between like-colored LEDs (Figure 2-60).

Screen resolution.The number of horizontal and vertical pixels that a device displays on the screen is referred to as screen resolution. The iPhone 7, for example, features a resolution of 750 x 1334. Another way to express resolution is pixels per inch (ppi). The 4.7-inch screen on an iPhone 7 with Apple’s Retina display technology has a resolution of 326 ppi.
◗Should I set my computer on its highest resolution? Most displays have a recommended resolution at which images are clearest and text is crispest. On laptops and desktops, however, you can change the resolution. In Windows, you can use the Control Panel or right-click the desktop and select Screen Resolution. In macOS, use the Apple icon to open System Preferences and choose Displays. At higher resolutions, text and objects may appear smaller, but the desktop appears more spacious. The two screens in Figure 2-61 help you compare the same display set at two different resolutions.

Try iT! What is the current setting for the resolution on your laptop or desktop? Is it the highest possible resolution?
◗How does a touchscreen work?Tablet computers, handheld devices, retail store self-checkouts, and ATMs display output and collect input from a touchscreen. Touchscreens display menus, scroll bars, and other controls. They can also display a virtual keyboard for devices that are not connected to a physical keyboard.
Touch events, such as taps, drags, and pinches, are sometimes called ges- tures. The coordinates for a touch event are processed in essentially the same way as a mouse click. For example, if you touch your iPad screen at the location of a button Iabeled Calendar, the area you touch generates coordinates and sends them to the processor. The processor compares the coordinates to the image displayed on the screen to find out what is at the coordinates, and then responds—in this case, by opening your appoint- ment calendar. The two most commonly used touchscreen technologies are resistive and capacitive (Figure 2-62).

QUlCKCHECK it was a cold day and you tried to use your smartphone while wearing gloves, but your gestures were ignored. The touchscreen on that device probably uses technology.

capacitive
resistive
virtual
DlGlTAL DEVlCES

◗What is a GPU? Display devices require graphics circuitry to gener- ate and transport the signals for displaying an image on the screen. One type of graphics circuitry, referred to as integrated graphics, is built into a computer's system board. A second option, called dedicated graphics, is graphics circuitry mounted on a small circuit board called a graphics card (or video card) like the one in Figure 2-63.

A graphics card contains a graphics processing unit (GPU) and special video memory, which stores screen images as they are processed but before they are displayed. A fast GPU and lots of video memory are the keys to lightning-fast screen updating for fast action games, 3D model- ing, and graphics-intensive desktop publishing (Figure 2-64).

PrinTerS The importance of printers has declined as digital distribution becomes more prevalent and cloud-based print services become more popular. Yet a printer can come in handy for creating printed documents, handouts, posters, and photos. Today’s best-selling multifunction printers use ink jet or laser technology and can also serve as scanners, copiers, and fax machines.
◗ How does an ink jet printer work? An ink jet printer has a nozzle-like print head that sprays ink onto paper to form characters and graphics. The print head in a color ink jet printer consists of a series of nozzles, each with its own ink cartridge (Figure 2-65).
Most ink jet printers use CMYK color, which requires only cyan (blue), magenta (pink), yellow, and black inks to create a printout that appears to contain thousands of colors.
Figure 2-65: ink jeT CMyk CArTriDgeS
Ink jet printers outsell all other types of printers because they are inexpensive and produce both color and black-and-white printouts. They work well for most home and small business applications. Ink jet technology also powers many photo printers, which are optimized to print high-quality images produced by digital cameras and scanners.
◗How do laser printers compare to ink jet printers? A laser printer like the one shown in Figure 2-66 uses the same technology as a photocopier to paint dots of light on a light-sensitive drum. Electrostatically charged ink is applied to the drum and then transferred to paper. A laser printer prints faster than an ink jet printer, but laser technology is more complex than ink jet technology, which accounts for the higher price of laser printers. A basic laser printer produces only blackand-white printouts. Color laser printers are available, but they are somewhat more costly than basic black-and-white models. Laser printers are often the choice for business printers, particularly for applications that produce a high volume of printed
◗What about 3d printers?
The technology that deposits ink on paper
is the foundation for 3D printers that deposit layers of plastic, resin, or metal that build into a three-dimensional object. 3D printing is technically called additive manufacturing. Consumers can use 3D printers to produce small toys, ornaments, and even simple electronic devices. These printers have been used to create wearable items, such as shoes, and replacement parts for household appliances. An important industrial use for 3D printers is prototyping new products, such as automobile headlights, smartphone cases, firearms, and even full-scale bicycles. Additive manufacturing is used to produce hearing aids and other medical devices that are custom fit or in other ways unique. Dental laboratories use 3D printing to produce crowns, bridges, and other dental appliances.
◗How do 3d printers work? There are several additive manufacturing technologies, but most consumer-grade 3D printers use a technology called filament deposit modeling (FDM) that melts a coiled filament and deposits it in layers that harden and form an object (Figure 2-67).

◗What are the filaments made from? Several types of filament are available. Polylactic acid (PLA) filament is versatile, and biodegradable because it is made from corn starch. Acrylonitrile butadiene styrene (ABS) filament is more durable and heat-resistant, making it suitable for printing objects that need to withstand some wear and tear. Polycarbonate (PC) filament is even sturdier and is used primarily for items that will be used in high-impact situations. Filaments cost about $10 per pound.
◗ What controls the printout? A 3D printed object is based on a 3D model that is essentially a 3D vector graphic. The model can be created using graphics software or it can be derived from a 3D scan of a real object. Modules are often stored in the STL file format. Several Web sites offer collections of STL files for 3D printing.
THlNGS
The utopian vision for the lnternet of Things (loT) is a busy hive of smart sensors that work behind the scenes to collect data and use it to improve—well—just about everything. All types of "things" equipped with smart sensors can monitor our hornes, cars, and workplaces. They can also monitor our habits and physical fitness and communicate with each other while doing so.
◗What are the basic features required for loT devices? loT devices require some way to communicate with other sensors and devices. That communication is handled by network technology, which is covered in the next module.
loT devices may include a microprocessor and memory if the device must process data, make decisions, or initiate an activity. A basic loT circuit board contains one or more sensors, a power source, a transmitter, and an antenna (Figure 2-68).

◗What types of smart sensors are available? The most popular loT sensors send alerts based on data they collect (Figure 2-69).

◗**What are the most popular sensors? Many smartphones, VR headsets, and automobile internal navigation systems incorporate three sensors: an accelerometer, a gyroscope, and a magnetometer. Figure 2-70 illustrates an lMU (inertial measurement unit) that packages these sensors into a single unit.

◗Where can I get loT devices? Smart sensors are available in elec- tronics stores, hardware stores, and online. Sensors can be purchased individually or in packages. Popular home monitoring packages, such as Apple's HomeKit, include cameras, thermostats, light bulbs, water sensors, door locks, and VOC air quality sensors.
◗Do sensors have security risks? Sensors themselves are not generally a security risk, but the data they collect can be used for unauthor— ized purposes. A smart thermostat can be used legitimately by a homeowner to remotely QUlCKCHECK track and adjust the temperature of a house or apartment. With approval, Which one of the following data from the thermostat might even be collected by the local power com- aspects of smart sensors on the pany and used to gaUQG usage levels. loT would be the least likely to Because the thermostat communicates using a wireless network, the signal pose a security riSk is subject to interception. An unauthorized person might monitor the signal a. Anonymized data to determine when a homeowner leaves the house (heat is turned down), arrives home (heat is turned up), or goes on vacation (heat remains down for several days). b. Data transmitted without encryption
When considering smart sensors, take care to understand where their data c' Data Stored on a Web S'te can be stored, who can access the data, and who can control the device. To d. Temperature sensors maximize security, select sensors that store data locally or on a secure site. supplied by your electric ln addition, confirm that all data is encrypted before it is transmitted and service provider stored, and ensure it can be controlled only by you.

AuTOnOMOuS vehiCleS There are drones in the sky, Roombas crisscrossing the floor, and cars speeding down the highway in Supercruise mode. The technology that allows these vehicles to operate autonomously or semi-autonomously requires an array of sensors communicating with an onboard computer.
◗exactly what is an autonomous vehicle? Cars, trucks, trains, drones, planes, and machines that are usually piloted by humans become autonomous as the vehicles, rather than the humans, take over control of speed, braking, and steering. Fully autonomous vehicles operate without a person at the controls. Semi-autonomous vehicles provide assistance to a human operator. Features available in semi-autonomous automobiles include adaptive cruise control, in-lane steering control, automatic parking, and collision avoidance systems, which take over some, but not all, driving tasks.
◗ How do autonomous vehicles make control decisions?
In general, autonomous vehicles use sense-plan-act algorithms that emerged with the development of robotic systems. These algorithms may be classified as artificial intelligence (AI) because they make decisions and carry out activities without human intervention. Sense-plan-act algorithms gather data, analyze it, and then carry out the required actions. Multiple sense-plan-act loops operate simultaneously. For example, in a self-driving car one loop may be sensing lane markings, while another loop is monitoring the distance to the vehicle ahead, and yet another loop is watching for suddenly appearing objects. Figure 2-71 provides additional details pertaining to sense-plan-act.

Try iT! Autonomous vehicles, such as self-driving cars, have limitations. Can you discover what type of pre-mapping is required before a Google car takes to the road?
◗What kinds of sensors keep an autonomous vehicle on the road? Lidar (light detection and radar) is a key input for the computer algorithms that steer an autonomous vehicle, but radar, sonar, infrared, GPS, cameras, and internal navigation systems also supply essential data (Figure 2-72).

带你读《计算机文化》之二：DIGITAL DEVICES

2DIGITAL DEVICES

DEVICES BASICS

DEVICES OPTION

PROCESSORS And MEMORYSECTION

STORAG

华章出版社

热门文章

最新文章

相关电子书

热门

活动广场

任务中心

开发者评测

高校计划

乘风者计划

训练营

阿里云MVP

话题

直播

下载

镜像站

技术资料

插件

带你读《计算机文化》之二：DIGITAL DEVICES

2DIGITAL DEVICES

DEVICES BASICS

DEVICES OPTION

PROCESSORS And MEMORYSECTION

STORAG

华章出版社

热门文章

最新文章

相关电子书