Memory

Memory consists of electronic components that store instructions waiting to be executed by the processor, data needed by those instructions, and the results of processing the data (information). Memory usually consists of one or more chips on the motherboard or some other circuit board in the computer.

 Memory stores three basic categories of items: (1)the operating system and other system software that control or maintain the computer and its devices; (2) application programs that carry out a specific task such as word processing; and (3) the data being processed by the application programs and resulting information. This role of memory to store both data and programs is known as the stored program concept.

Bytes and Addressable Memory

 A byte (character) is the basic storage unit in memory. When application program instructions and data are transferred to memory from storage devices, the instructions and data exist as bytes. Each byte resides temporarily in a location in memory that has an address. An address simply is a unique number that identifies the location of a byte in memory. To access data or instructions in memory, the computer references the addresses that contain bytes of data.

Memory Sizes

 Manufacturers state the size of memory and storage devices in terms of the number of bytes the chip or device has available for storage. Recall that storage devices hold data, instructions, and formation for future use, while most memory holds these items temporarily. A kilobyte (KB or K) is equal to exactly 1,024 bytes. To simplify memory and storage definitions, computer users often round a kilobyte down to 1,000 bytes. For example, if a memory chip can store 100 KB, it can hold approximately 100,000 bytes (characters). A megabyte (MB) is equal to approximately 1 million bytes. A gigabyte (GB) equals approximately 1 billion bytes. A terabyte (TB) is equal to approximately 1 trillion bytes.

Types of Memory

 The system unit contains two types of memory: volatile and nonvolatile. When the computer's power is turned off, volatile memory loses its contents. Nonvolatile memory, by contrast, does not lose its contents when power is removed from the computer. Thus, volatile memory is temporary and nonvolatile memory is permanent. RAM is the most common type of volatile memory. Examples of nonvolatile memory include ROM, flash memory, and CMOS. The following sections discuss these types of memory.

RAM

 Users typically are referring to RAM when discussing computer memory. RAM (random access memory), also called main memory, consists of memory chips that can be read from and written to by the processor and other devices. When you turn on power tro a computer, certain operating system files (such as the files that determine how the desktop appears) load into RAM from a storage device such as a hard disk. These files remain ion RAM as long as the computer has continuous power. As additional programs and data are requested, they also load into RAM from storage.

 The processor interprets and executes a program's instructions while the program is in RAM. During this time, the contents of RAM may change. RAM can accommodate multiple programs simultaneously.

 Most RAM is volatile, which means it loses its contents when the power is removed from the computer. For this reason, you must save any data, instructions, and information you may need in the future. Saving is the process of copying data, instructions, and information from RAM to a storage device such as a hard disk.

 Three basic types of Ram chips exist: dynamic RAM, static RAM, and magnetoresistive RAM.

• Dynamic RAM (DRAM pronounced DEE-ram) chips must be re-energized constantly or they lose their contents. Many variations of DRAM chips exist, most of which are faster than the basic DRAM. Most personal computers today use some form of SDRAM chips or RDRAM chips.
• Static RAM (SRAM pronounced ESS-ram) chips are faster and more reliable than any variation of DRAM chips. These chips do not have to be re-energized as often as DRAM chips, thus the term static. SRAM chips, however, are much more expensive than DRAM chips. Special applications such as cache use SRAM chips. A later section in this chapter discusses cache.
• A newer type of RAM, called magnetoresistive RAM (MRAM pronounced EM-ram), stores data using magnetic charges instead of electrical charges. Manufacturers claim that MRAM has greater storage capacity, consumes less power, and has faster access times than electronic RAM. Also, MRAM retains its contents after power is removed from the computer, which could prevent loss of data for users. As the cost of MRAM declines, experts predict MRAM could replace both DRAM and SRAM.

 Ram chips usually reside on a memory module, which is a small circuit board. Memory slots on the motherboard hold memory modules. Three types of memory modules are SIMMs, DIMMs, and RIMMs. A SIMM (single inline memory module) has pins on oppositesides of the circuit board that connect together to form a single set of contacts. With a DIMM (dual inline memory module), by contrast, the pins on opposite sides of the circuit board do not connect and thus form two sets of contacts. SIMMs and DIMMs typically hold SDRAM chips. A RIMM (Rambus inline memory module) houses RDRAM chips.

RAM Configurations  The amount of RAM necessary in a computer often depends on the types of software you plan to use. A computer executes programs that are in RAM. Think of RAM as the workplace on the top of your desk. Just as the top of your desk needs a certain amount of space to hold papers, a computer needs a certain amount of memory to store programs, data, and information. The more RAM a computer has, the faster the computer will respond.

 Retail software typically indicates the minimum amount of RAM it requires. If you want the software to perform optimally, usually you need more than the minimum specifications for the software.

Cache

 Most of today's computers improve their processing times with cache (pronounced cash). Two types of cache are memory cache and disk cache.

 Memory cache helps speed the processes of the computer because it stores frequently used instructions and data. Most personal computers today have two types of memory cache: L1 cache and L2 cache. Some also have L3 cache.

• L1 cache is built directly in the processor chip. L1 cache usually has a very small capacity, ranging from 8 KB to 128 KB. The more common sizes for personal computers are 32 KB or 64 KB.
• L2 cache is slightly slower than L1 cache but has a much larger capacity, ranging from 64 KB to 16 MB. When discussing cache, most users are referring to L2 cache. Current processors include advanced transfer cache (ATC), a type of L2 cache built directly on the processor chip.
• L3 cache is a cache on the motherboard that is separate from the processor chip. L3 cache exists only on computers that L2 advanced transfer cache. Personal computers often have up to 8 MB of L3 cache; servers and workstations have from 8 MB to 24 MB of L3 cache.

 Cache speeds up processing time because it stores frequently used instructions and data. When the processor needs an instruction or data, it searches memory in this order: L1 cache, then L2 cache, then L3 cache (if it exits), then RAM – with a greater delay in processing for each level of memory it must search. If the instruction or data is not found in memory, then it must search a slower speed storage medium such as a hard disk or optical disc.

 Windows users can increase the size of cache through Windows Ready Boost, which can allocate available storage space on removable flash memory devices as additional cache. Examples of removable flash memory include USB flash drives, CompactFlash cards, and SD (Secure Digital) cards.

ROM

 Read-only memory (ROM) refers to memory chips storing permanent data and instructions. The data on most ROM chips cannot be modified – hence, the name read-only. ROM is nonvolatile, which means its contents are not lost when power is removed from the computer. In addition to computers, many devices contain ROM chips. For example, ROM chips in printers contain data for for fonts.

 Manufacturers of ROM chips often record data, instructions, or information on the chips when they manufacture the chips. These ROM chips, called firmware, contain permanently written data, instructions, or information.

 A PROM (programmable read-only memory) chip is a blank ROM chip on which a programmer can write permanently. Programmers use microcode instructions to program a PROM chip. Once a programmer writes the microcode on the PROM chip, it functions like a regular ROM chip and cannot be erased or changed.

 A variation of the PROM chip, called an EEPROM (electrically erasable programmable read-only memory) chip, allows a programmer to erase the microcode with an electric signal.

Flash Memory

 Flash memory is a type of nonvolitale memory that can be erased electronically and rewritten, similar to EEPROM. Most computers use flash memory to hold their startup intructions because it allows the computer easily to update its contents. For example, when the computer changes from standard time to daylight savings time, the contents of a flash memory chip (and the real-time clock chip) change to reflect the new time.

 Flash memory chips also store data and programs on many mobile computers and devices, such as smart phones, portable media players, PDAs, printers, digital cameras, automotive devices, digital voice recorders, and pagers.

 When you enter names and addresses in a smart phone or PDA, a flash memory chip stores the data. Some portable media players store music on flash memory chips; others store music on tiny hard disks or flash memory cards. Flash memory cards contain flash memory on a removable device instead of a chip.

CMOS

 Some RAM chips, flash memory chips, and other memory chips use complementary metal-oxide semiconductor (CMOS pronounced SEE-moss) technology because it provides high speeds and consumes little power. CMOS technology uses battery power to retain information even when the power to the computer is off. Battery-backed CMOS memory chips, for example, can keep the calendar, date, and time current even when the computer is off. The flash memory chips that store a computer's startup information often use CMOS technology.

Memory Access Times

 Access time is the amount of time it takes the processor to read data, instructions, and information from memory. A computer's access time directly affects how fast the computer process data. Accessing data in memory can be more than 200,000 times faster than accessing data on a hard disk because of the mechanical motion of the hard disk.

 Today's manufacturers use a variety of terminology to state access times. Some use fractions of a second which for memory occurs in nanoseconds. A nanosecond (abbreviated ns) is one billionth of a second. A nanosecond is extremely fast. In fact, electricity travels about one foot in a nanosecond.

 Other manufacturers state access time in MHz; for example, 800 MHz DDR2 SDRAM. If a manufacturer states access time in megahertz, you can convert it to nanoseconds by dividing 1 billion ns by the megahertz number. For example, 800 MHz equals approximately 1.25 ns (1,000,000,000/800,000,000).

 The access time (speed) of memory contributes to the overall performance of the computer. Standard SDRAM chips can have access times up to 133 MHz (about 7.5 ns), and access times of DDR SDRAM chips reach 266 MHz, DDR2 chips reach 800 MHz, and DDR3 chips reach 1600 MHz. The higher the megahertz, the faster the access time; conversely, the lower the nanoseconds, the faster the access time. The faster RDRAM chips can have access times up to 1600 MHz (about 0.625 ns). ROM access times range from 25 to 250 ns.

 While access times of memory greatly affect overall computer performance, manufacturers and retailers usually list a computer's memory in terms of its size, not its access time. Thus, an advertisement might describe a computer as having 2 GB of SDRAM upgraded to 4 GB.

Data Representation

To understand how a computer process data, you should know how a computer represents data, you should know how a computer represents data. People communicate through speech by combining words into sentences. Human speech is analog because it uses continuous (wave form) signals that vary in strength and quality. Most computers are digital. They recognize only two discrete states: on and off. This is because computers are electronic devices powered by electricity, which also has only two states: on and off.

 The two digit, 0 and 1, easily can represent these two states. The digit 0 represents the electronic state of off (absence of an electronic charge). The digit 1 represents the electronic state of on (presence of an electronic charge).

 When people count, they use the digits in the decimal system (0 through 9). the computer, by contrast, uses a binary system because it recognizes only two states. The binary system is a number system that has just two unique digits, 0 and 1, called bits. A bit (short for binary digit) is the smallest unit of data the computer can process. By itself, a bit is not very informative.

 When 8 bits are grouped together as a unit, they form a byte. A byte provides enough different combinations of 0s and 1s to represent 256 individual characters. These characters include numbers, uppercase and lowercase letters of the alphabet, punctuation marks, and others, such as the letters of the Greek alphabet.

 The combinations of 0s and 1s that represent characters are defined by patterns called a coding scheme. In one coding scheme, the number 4 is represented as 00110100, the number 6 as 00110110, and the capital letter E as 01000101. ASCII which stands for American Standard Code for Information Interchange is the most widely used coding scheme to represent data.

 The ASCII coding scheme is sufficient for English and Western European languages but is not large enough for Asian and other languages that use different alphabets. Unicode is a 16-bit coding scheme that has the capacity of representing more than 65,000 characters and symbols. The Unicode coding scheme is capable of representing almost all the world's current written languages, as well as classic and historical languages. To allow for expansion, Unicode reserves 30,000 codes for future use and 6,000 codes for private use. Unicode is implemented in several operating systems, including Windows, Mac Os, and Linux. Unicode-enabled programming languages and software include Java, XML, Microsoft Office, and Oracle.

 Coding schemes make it possible for humans to interact with a digital computer that processes only bit. When you press a key on a keyboard, a chip in the keyboard converts the key's electronic signal into a special code that is sent to the system unit. Then, the system unit converts the code into a binary form the computer can process and store it in memory. Every character is converted to its corresponding byte. The computer then processes the data as bytes, which actually is a series of on/off electrical states. When processing is finished, software converts the byte into a human-recognizable number, letter of the alphabet, or special character that is displayed on a screen or is printed. All of these conversions take place so quickly that you do not realize they are occurring.

 Standards, such as those defined by ASCII and Unicode, also make it possible for components in computers to communicate with each other successfully. By following these and other standards, manufacturers can produce a component and be assured that it will operate correctly in a computer.      

Processor

 The processor, also called the central processing unit (CPU), interprets and carries out the basic instructions that operate a computer. The processor significantly impacts overall computing power and manages most of a computer's operations. On larger computers, such as mainframes and supercomputers, the various functions performed by the processor extend over many separate chips and often multiple circuit boards. On a personal computer, all functions of the processor usually are a single chip. Some computer and chip manufacturers use the term microprocessor to refer to a personal computer processor chip.

 Most processor chip manufacturers now offer multi-core processors. A processor core, or simply core, contains the circuitry necessary to execute instructions. The operating system views each processor core as a separate processor. A multi-core processor is a single chip with two or more separate processor cores. Two common multi-core processor are dual-core and quad-core. A dual-core processor is a chip that contains two separate processor cores. Similarly, a quad-core processor is a chip with four separate processor cores.

 Each processor core on a multi-core processor generally runs at a slower clock speed than a single-core processor, but multi-core processors typically increase overall performance. For example, although a dual-core processor does not double the processing speed of a single-core processor, it can approach those speeds. The performance increase is especially noticeable when users are running multiple programs simultaneously such as antivirus software, spyware remover, e-mail program, instant messaging, media player, disc burning software, and photo editing software. Multi-core processors also are more energy efficient than separate multiple processor, requiring lower levels of power consumption and emitting less heat in the system unit.

 Processors contain a control unit and an arithmetic logic unit (ALU). These two components work together to perform processing operations.

The Control Unit

 The control unit is the component of the processor that directs and coordinates most of the operations in the computer. The control unit has a role much like a traffic cop: it interprets each instruction issued by a program and then initiates the appropriate action to carry out the instruction. Types of internal components that the control unit directs include the arihtmetic/logic unit, registers, and buses.

The Arithmetic Logic Unit

 The arithmetic logic unit (ALU), another component of the processor, performs arithmetic, comparison, and other operations.

 Arithmetic operations include basic calculations such as addition, subtraction, multiplication, and division. Comparison operations involve comparing one data item with another to determine wheter the first item is greater than, equal to, or less than the other item. Depending on the result of the comparison, different actions may occur. For example, to determine if an employee should receive overtime pay, software instructs the ALU to compare the number of hours an employee worked during the week with the regular time hours allowed (e.g., 40 hours). If the hours worked exceed 40, for example, software instructs the ALU to perform calculations that compute the overtime wage.

Machine Cycle

 For every instruction, a processor repeats a set of four basic operations, which comprise a machine cycle: (1) fetching, (2) decoding, (3) executing, and, if necessary (4) storing. Fetching is the process of obtaining a program instruction or data item from memory. The term decoding refers to the process of translating the instruction into signals the computer can execute. Executing is the process of carrying out the commands. Storing, in this context, mean writing the result to memory (not to a storage medium).

 In some computers, the processor fetches, decodes, executes, and stores only one instruction at a time. In these computers, the processor waits until an instruction completes all four stages of the machine cycle (fetch, decode, execute, and store) before beginning work on the next instruction.

 Most of today's personal computers support a concept called pipelining. With pipelining, the processor begins fetching a second instruction before it completes the machine cycle for the first instruction. Processors that use pipelining are faster because they do not have to wait for one instruction to complete the machine cycle before fetching the next. Think of a pipeline as an assembly line. By the time the first instruction is in the last stage of the machine cycle, three other instructions could have been fetched and started through the machine cycle.

Registers

 A processor contains small, high-speed storage locations, called registers, that temporarily hold data and instructions. Registers are part of the processor, not part of memory or a permanent storage device. Processors have many different types of registers, each with a specific storage function. Register functions include storing the location from where an instruction was fetched, storing an instruction while the control unit decodes it, storing data while the ALU computes it, and storing the results of a calculation.

The System Clock

 The processor relies on a small quartz crystal circuit called the system clock to control the timing of all computer operations. Just as your heart beats at a regular rate to keep your body functioning, the system clock generates regular electronic pulses, or ticks, that set the operating pace of components of the system unit.

 Each tick equates to a clock cycle. In the past, processor used one or more clock cycles to execute each instruction. Processors today often are superscalar, which means they can execute more then one instruction per clock cycle.

 The pace of the system clock, called the clock speed, is measured by the number of ticks per second. Current personal computer processors have clock speeds in the gigahertz range. Giga is a prefix that stands for billion, and a hertz ione cycle per second. Thus, one gigahertz (GHz) equals one billion ticks of the system clock per second. A computer that operates at 3 GHz has 3 billion (giga) clock cycles in oen second (hertz).

 The faster the clock speed, the more instruction the processor can execute per second. The speed of the system clock has no effect on devices such as a printer or disk drive. The speed of the system clock is just one factor that influences a computer's performance. Other factors, such as the type of processor chip, amount of cache, memory access time, bust width, and bus clock speed, are discussed later.

Comparison of Personal Computer Processor

 The leading manufacturers of personal computer chips are Intel and AMD. These manufacturers often identify their processor chips by a model name or model number. High-performance personal computers today may use a processor in the Intel Core family. Less expensive, basic personal computers may use a brand of Intel processor in the Pentium or Celeron family. The Xeon and Itanium families of processors are ideal for workstations and low-end servers.

 AMD is the leading manufacturer of Intel-compatible processors, which have an internal design similar to Intel processors, perform the same functions, and can be as powerful, but often are less expensive.

 In the past, chip manufacturers listed a processor's clock speed in marketing literature and advertisements. As previously mentioned, though, clock speed is only one factor that impacts processing speed in today's computers. To help consumers evaluate various processors, manufacturers such as Intel and AMD now use a numbering scheme that more accurately reflects the processing speed of their chips.

 Processor chips include technologies to improve processing performance, for example, to improve performance of multimedia and 3-D graphics. Most of Intel's processor chips also include vPro technology, which provides the capability to track computers hardware and software, diagnose and resolve computer problems, and secure computers form outside threats.

 As mentioned earlier, many personal computer processors are multi-core, with the processor cores working simultaneously on related instructions. These related instructions, called a thread, can be independent or part of a larger task. Software written to support multiple threads, called a multi-threaded program, run much faster than those in no threaded environments.

 Processors for traditional notebook computers and Tablet PCs also include technology to optimize and extend battery life, enhance security, and integrate wireless capabilities. For example, Intel's Centrino 2 mobile technology, which may have a Pro designator depending on its capabilities, integrates wireless functionality in notebook computers and Tablet PCs. Netbooks, smart phones, and other smaller mobile devices often use more compact processor that consume less power, yet offer high performance.

 Another type of processor, called system-on-a-chip, integrates the functions of a processor, memory, and a video card on a single chip. Lower-priced personal computers, Tablet PCs, networking devices, portable media players, and game consoles sometimes have a system-on-a-chip processor. The goal of system-on-a-chip manufacturers is to create processors that have faster clock speeds, consume less power, are small, and are cost effective.

Buying a Personal Computer

 If you are ready to buy a new computer, the processor you select should depend on how you plan to use the computer. To realize greater processing performance, you may want to choose a multi-core processor.

 Instead of buying an entirely a new computer, you might be able to upgrade your processor to increase the computer's performance. Be certain the processor you by is compatible with your computer's motherboard; otherwise, you will have to replace the motherboard, too. Replacing a processor is a fairly simple process, whereas replacing a motherboard is much more complicated.

Processor Cooling

 Processor chips generate quite a bit of heat, which could cause the chip to burn up.although the computer's main fan generates airflow, many of today's personal computer processors require additional cooling. Heat sinks/pipes and liquid cooling technologies often are used to help dissipate processor heat.

 A heat sink is a small ceramic or metal component with fins on its surface that absorbs and disperses heat produced by electrical components such as a processor. Some heat sinks are packaged as part of a processor chip. Others are installed on the top or the side of the chip. Because a heat sink consumes extra space, a smaller device called a heat pipe cools processors in notebooks and Tablet PCs.

 Some computers use liquid cooling technology to reduce the temperature of a processor. Liquid cooling technology uses a continuous flow of fluid(s), such as water and glycol, in a process that transfers the heated fluid away from the processor to a radiator-type grill, which cools the liquid, and then returns the cooled fluid to the processor.

 Some mobile computers and devices often have Low Voltage or Ultra Low Voltage (ULV) processors, which have such low power demands that they do not require additional cooling.

Parallel Processing

 Parallel processing is a method that uses multiple processors simultaneously to execute a single program or task. Parallel processing divides a single problem into portions so that multiple processors work on their assigned portion of the problem at the same time. Parallel processing requires special software that recognizes how to divide the problem and then bring the results back together again.

 Some personal computers implement parallel processing with dual-core processors or multi-core processors. Others have two or more separate processor chips, respectively called dual processor or multiprocessor computers.

 Massively parallel processing is large scale parallel processing that involves hundreds or thousands of processors. Supercomputers use massively parallel processing for applications such as artificial intelligence and weather forecasting.     

The System Unit

Whether you are a home user or a business user, you most likely will purchase a new computer or upgrade an existing computer at some time in the future. Thus, you should understand the purpose of each component in a computer. A computer includes devices used for input, processing, output, storage, and communications. Many of these components are part of the system unit.

 The system unit is a case that contains electronic components of the computer used to process data. System units are available in a variety of shapes and sizes. The case of the system unit, sometimes called the chassis, is made of metal or plastic and protects the internal electronic components from damage. All computers and mobile devices have a system unit.

 On desktop personal computers, the electronic components and most storage devices are part of the system unit. Other devices, such as the keyboard, mouse, microphone, monitor, printer, USB flash drive, scanner, Web cam, and speakers, normally occupy space outside the system unit. An all-in-one desktop personal computer is an exception, which houses the monitor and the system unit in the same case. The trend is toward a smaller form factor, or size and shape, of the desktop personal computer system unit.

 On most notebook computers, including netbooks, the keyboard and pointing device often occupy the area on the top of the system unit, and the display attaches to the system unit by hinges. The location of the system unit on a Tablet PC varies, depending on the design of the Tablet PC. With the slate Tablet PC, which typically does not include a keyboard, the system unit is behind the display. On a convertible Tablet PC, by contrast, the system unit is positioned below a keyboard, providing functionality similar to a traditional notebook computer or netbook. The difference is the display attaches to the system unit with a swivel-type hinge, which enables a user to rotate the display and fold it down over the keyboard to look like a slate Tablet PC. The system unit on an Ultra-Mobile PC, a smart phone, and a PDA usually consumes the entire device. On these mobile computers and devices, the display often is built into the system unit.

 With game consoles, the input and output devices, such as controllers and television, reside outside the system unit. On handheld game consoles, portable media players, and digital cameras, by contrast, the packaging around the system unit houses the input devices and display.

 At some point, you might have to open the system unit on a desktop personal computer to replace or install a new electronic component. For this reason, you should be familiar with the electronic components of a system unit. Some of these components include the processor, memory, adapter cards, drive bays, and the power supply.

 The processor interprets and carries out the basic instructions that operate a computer. Memory typically holds data waiting to be executed. The electronic components and circuitry of the system unit, such as the processor and memory, usually are part of or are connected to a circuit board called the motherboard. Many current motherboards also integrate sound, video, and networking capabilities.

 Adapter cards are circuit boards that provide connections and functions not built into the motherboard or expand on the capability of features integrated into the motherboard. For example, a sound card and a video card are two types of adapter cards found in some desktop personal computers today.

 Devices outside the system unit often attach to ports on the system unit by a connector on a cable. These devices may include a keyboard, mouse, microphone, monitor, printer, scanner, USB flash drive, card reader/writer, Web cam, and speakers. A drive bay holds one or more disk drives. The power supply converts electricity from a power cord plugged in a wall outlet into a form that can be used by the computer.

The Motherboard

 The motherboard, sometimes called a system board, is the main circuit board of the system unit. Many electronic components attach to the motherboard; others are built into it.

 A computer chip is a small piece of semi-conducting material, usually silicon, on which integrated circuits are etched. An integrated circuit contains many microscopic pathways capable of carrying electrical current. Each integrated circuit can contain millions of elements such as resistors, capacitors, and transistors. A transistor, for example, can act as an electronic switch that opens or closes the circuit for electrical charges. Today's computer chips contain millions or billions of transistors. Most chips are in bigger than one-half-inch square. Manufacturers package chips so that the chips can be attached to a circuit board such as a motherboard or an adapter card.     

Learning Tools for Application Software

Learning how to use application software effectively involves time and practice. To assist in the learning process, many programs include an integrated Help feature. Online Help is the electronic equivalent of a user manual. When working with a program, you can use online Help to ask a question or access the Help topics in subject or alphabetical order. Most online Help also links to Web sites that offer Web-based Help, which provides updates and more comprehensive resources to respond to technical issues about software.

 If you want to learn more about a particular program from a printed manual, many books are available to help you learn to use the features of personal computer programs. These books typically are available in bookstores and software stores.

 Many colleges and schools provide training on several of the programs discussed.

Web-Based Training

 Web-based training (WBT) is a type of CBT (computer-based training) that uses Internet technology and consists of application software on the Web. Similar to CBT, WBT typically consists of self-directed, self-paced instruction about a topic. WBT is popular in business, industry, and schools for teaching new skills or enhancing existing skills of employees, teachers, or students. When using a WBT product, students actively become involved in the learning process instead of remaining passive recipients of information.

 Many Web sites offer WBT to the general public. Such training covers a wide range of topics, from how to change a flat tire to creating documents in Word. Many of these Web sites are free. Others require registration and payment to take the complete Web-based course.

 WBT often is combined with other materials for distance learning and e-learning. Distance learning (DL) is the delivery of education at one location while the learning takes place at other locations. DL courses provide time, distance, and place advantages for students who live far from a college campus or work full time. These courses enable students to attend class from anywhere in the world and at times that fit their schedules. Many national and international companies offer DL training. These training courses eliminate the costs of airfare, hotels, and meals for centralized training sessions.

 E-learning, short for electronic learning, is the delivery of education via some electronic method such as the Internet, networks, or optical discs. To enhance communications, e-learning systems also may include video conferencing, e-mail, blogs, wikis, newsgroups, chat rooms, and groupware.

 E-learning providers often specialize in presenting instructors with the tools for preparation, distribution, and management of Dl courses. These tools enable instructors to create rich, educational Web-based training sites and allow the students to interact with a powerful Web learning environment. Through the training site, students can check their progress, take practice tests, search for topics, send e-mail messages, and participate in discussions and chats. 

Application Software for Communications

One of the main reasons people use computers is to communicate and share information with others. Some communications software is considered system software because it works with hardware and transmission media. Other communications software makes users more productive and/or assists them with personal tasks, and thus, is considered application software.