Download Networking basic knowledge and more Study notes Computer science in PDF only on Docsity!
ObjectivesObbjjectiives
Introduction
to Computers
and How to Purchase
Computers and Mobile Devices
After completing this chapter, you will be able to: 1 Define the term computer and discuss the four basic computer operations: input, process, output, and storage
2 Define data and information
3 Identify the differences among desktop computers, notebook computers, and mobile devices
4 Explain the primary components of the computer and their use
5 Describe the use of hard disks, flash memory, optical discs, and other storage media
6 Discuss computer software and explain the difference between system software and application software 7 Identify several types of application software 8 Discuss the Internet and World Wide Web 9 Describe various types of Internet and network attacks and how to protect against them 10 Explain how to purchase computers and mobile devices
COM 2 Introduction to Computers
printer (output device)
scanner (input device)
USB flash drive (storage device)
modem (communications device) memory cards (storage device)
card reader/writer (storage device)
speakers (output device)
monitor (output device) screen
microphone (input device)
mouse (input device)
system unit (processor, memory, and storage devices)
Web cam (input device)
optical disc drive (storage device)
hard disk drive (storage device)
external hard disk (storage device)
keyboard (input device)
What Is a Computer?
Computers are everywhere: at work, at school, and at home. In the workplace, employees use computers to create correspondence such as e-mail messages, memos, and letters; manage calendars; calculate payroll; track inventory; and generate invoices. At school, teachers use computers to assist with classroom instruction. Students use computers to complete assignments and research. People also spend hours of leisure time using a computer. They play games, communicate with friends and relatives online and using e-mail, purchase goods online, converse in chat rooms, listen to music or radio broadcasts, watch or create videos and movies, read books and magazines, share stories, research genealogy, retouch photos, and plan vacations. At work, at school, and at home, computers are helping people do their work faster, more accurately, and in some cases, in ways that previously would not have been possible. A computer is an electronic device, operating under the control of instructions stored in its own memory, that can accept data (input), process the data according to specified rules (process), produce results (output), and store the results (storage) for future use. Generally, the term is used to describe a collection of electric, electronic, and mechanical components known as hardware. Figure 1 shows some common hardware components. These components are discussed in more depth later in this chapter.
Figure 1 Common computer hardware components include the keyboard, mouse, microphone, scanner, Web cam, printer, monitor, speakers, system unit, hard disk drive, external hard disk, optical disc drive(s), USB flash drive, card reader/writer, memory cards, and modem.
Computers For more information, visit scsite.com/ic8/weblink and then click Computers.
COM 4 Introduction to Computers
Figure 3 Most devices connected to the computer communicate with the processor to carry out a task. When a user starts a program, for example, its instructions transfer from a storage device to memory. Data needed by the program enters memory either from an input device or a storage device. The processor interprets and executes instructions in memory and also performs calculations on the data in memory. Resulting information is stored in memory, from which it can be sent to an output device or a storage device for future access, as needed.
OUTPUT DEVICES
PROCESSOR
INPUT DEVICES MEMORY
STORAGE DEVICES
instructions data information
instructions data information
data information
Personal Computers and Mobile Devices
A personal computer is a computer that can perform all of its input, processing, output, and storage activities by itself. A personal computer contains a processor, memory, and one or more input, output, and storage devices. Personal computers also often contain a communications device. A mobile computer is a personal computer you can carry from place to place. Similarly, a mobile device is a computing device small enough to hold in your hand. The most popular type of mobile computer is the notebook computer.
Desktop Computers
A desktop computer is designed so that the system unit, input devices, output devices, and any other devices fit entirely on or under a desk or table (Figure 4). In some models, the monitor sits on top of the system unit, which is placed on the desk. The more popular style of system unit is the tall and narrow tower, which can sit on the floor vertically.
Notebook Computers
A notebook computer , also called a laptop computer , is a portable, personal computer often designed to fit on your lap (Figure 5). These computers are thin and lightweight, yet can be as powerful as the average desktop computer. A netbook , which is a type of notebook computer, is smaller, lighter, and often not as powerful as a traditional notebook computer. Resembling a letter-sized slate, the Tablet PC is a special type of notebook computer that allows you to write or draw on the screen using a digital pen.
Mobile Devices
Mobile devices, which are small enough to carry in a pocket, usually store programs and data permanently on memory inside the system unit or on small storage media such as memory cards. You often can connect a mobile device to a personal computer to exchange information. Three popular types of mobile devices are smart phones, portable media players, and digital cameras.
Figure 4 A desktop computer.
Figure 5 A traditional notebook computer.
keyboard
display
optical disc drive
hinge
Figure 3 shows how the components of a computer interact to carry out a task. The following sections describe the types of personal computers and mobile devices, as well as their primary components (input devices, processor, memory, output devices, and communications devices).
Introduction to Computers COM 5
A smart phone is a phone that can connect to the Internet and usually also provides personal information management functions such as a calendar, an appointment book, an address book, a calculator, and a notepad (Figure 6). A portable media player is a mobile device on which you can store, organize, and play digital media (shown in Figure 1 on page COM 2). For example, you can listen to music; watch videos, movies, and television shows; and view photos on the device’s screen. A digital camera is a device that allows users to take pictures and store the photographed images digitally, instead of on traditional film (shown in Figure 1). Digital cameras typically allow users to review, and sometimes modify, images while they are in the camera.
Input Devices
An input device is any hardware component that allows you to enter data and instructions into a computer. Depending on your particular program and requirements, the input device you use may vary. Five widely used input devices are the keyboard, mouse, microphone, scanner, and Web cam (shown in Figure 1). The two primary input devices used are the keyboard and the mouse.
Keyboard
A keyboard is an input device that contains keys users press to enter data and instructions into the computer. All desktop computer keyboards have a typing area that includes the letters of the alphabet, numbers, punctuation marks, and other basic keys. Many desktop computer keyboards also have a numeric keypad on the right side of the keyboard. Most of today’s desktop computer keyboards are enhanced keyboards. An enhanced keyboard has 12 or more function keys along the top and a set of arrow and additional keys between the typing area and the numeric keypad (Figure 7). Function keys are special keys programmed to issue instructions to a computer.
Figure 6 A smart phone is a popular mobile device.
Figure 7 On a desktop computer keyboard, you type using keys in the typing area and on the numeric keypad.
WINDOWS key
typing area
wrist rest
APPLICATION key arrow keys
F3 key
media controls
function keys
Internet controls
additional keys
keyboard
numeric CTRL key keypad
NUM LOCK key
CTRL key ALT key ALT key
Input Devices For more information, visit scsite.com/ic8/weblink and then click Input Devices.
Introduction to Computers COM 7
Most notebook computers have a touchpad , a small, flat, rectangular pointing device near the keyboard that allows you to move the pointer by sliding a fingertip on the surface of the pad (Figure 10).
Other Input for Mobile Devices Most mobile devices, such as smart phones and PDAs, and some
notebook computers, such as Tablet PCs, use a variety of alternatives for entering data and instruc- tions (Figure 11). One of the more popular input devices for mobile devices is the stylus. Some have touch screens, enabling you to touch the screen to perform tasks.
enter text messages via a wireless keyboard
transfer data and instructions to and from the computer and phone by connecting it to the computer with a cable
take a picture using the digital camera built into the back of the phone
obtain maps and directions on the phone by attaching this navigation receiver to your vehicle’s window
use one end of the stylus to write on the phone’s screen and the other end as a ballpoint pen
speak into the microphone that wirelessly communicates with the phone
Figure 11 Besides a touch screen and basic stylus, users have a variety of other options for entering data and instructions into a smart phone.
Figure 10 Most notebook computers have a touchpad that allows a user to control the movement of the pointer.
touchpad
COM 8 Introduction to Computers
Figure 12 The system unit on a typical personal computer consists of numerous electronic components, some of which are shown in this figure. The sound card and video card are two types of adapter cards. processor
memory module
sound card
video card
power supply
System Unit
The system unit is a case that contains electronic components of the computer used to process data (Figure 12). System units are available in a variety of shapes and sizes. The case of the system unit, also called the chassis, is made of metal or plastic and protects the internal components from damage. 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. The sound card and video card shown in Figure 12 are examples of adapter cards, which are circuit boards that provide connections and functions not built into the motherboard or expand on the capability of features integrated into the motherboard.
Processor
The processor (bottom of Figure 12), also called the central processing unit ( CPU ), interprets and carries out the basic instructions that operate a computer. Processors contain a control unit and an arithmetic/logic unit. The control unit directs and coordinates most of the operations in the computer. The arithmetic/logic unit ( ALU ) performs arithmetic, comparison, and other operations. On a personal computer, all functions of the processor usually are on a single chip. A computer chip is a small piece of semiconducting material that contains many microscopic pathways capable of carrying electrical current. Today’s processors can perform some operations in less than the time it takes to blink your eye.
Memory
Memory consists of electronic components that store instructions waiting to be executed and data needed by those instructions. Most memory keeps data and instructions temporarily, which means its contents are erased when the computer is shut off. When discussing computer memory, users typically are referring to RAM. Also called main memory, RAM (random access memory) consists of memory chips that can be read from and written to by the processor and other devices. These chips are placed on a memory module (lower left of Figure 12) that fits in a slot on the motherboard in the system unit. The amount of memory in computers is measured in kilobytes, megabytes, gigabytes, or tera- bytes. A byte usually stores one character, such as the letter A. One kilobyte ( KB or K ) equals exactly 1,024 bytes, and one megabyte ( MB ) equals approximately one million bytes. One gigabyte ( GB ) equals approximately one billion bytes, and one terabyte ( TB ) equals approximately
Memory For more information, visit scsite.com/ic8/weblink and then click Memory.
drive bay
Processor For more information, visit scsite.com/ic8/weblink and then click Processor.
system unit
COM 10 Introduction to Computers
Storage Devices
A storage device is the computer hardware that records and/or retrieves items to and from storage media. A storage medium (media is the plural) is the physical material on which a computer keeps data, instructions, and information. Three common types of storage media are hard disks, flash memory, and optical discs.
Figure 16 Notebook computers, PDAs, smart phones, handheld game consoles, portable media players, and digital cameras have color LCD screens.
notebook computer
PDA
smart phone
portable media player (^) digital camera
handheld game console
Display Devices
A display device is an output device that visually conveys text, graphics, and video information. A monitor is a display device that is packaged as a separate peripheral. A widely used monitor is an LCD monitor. The LCD monitor shown in Figure 15 uses a liquid crystal display to produce images on the screen. The surface of the screen of an LCD monitor is com- posed of individual picture elements called pixels. Resolution is the number of horizontal and vertical pixels in a display device. For example, a screen set to a resolution of 1440 3 900 pixels displays up to 1440 pixels per horizontal row and 900 pixels per vertical row, for a total of 1,296,000 pixels to create a screen image. A higher resolution provides a smoother, sharper, clearer image. Mobile computers such as notebook computers, including netbooks and Tablet PCs, and mobile devices such as smart phones, portable media players, PDAs, handheld game consoles, and digital cameras, have built-in LCD screens (Figure 16).
Figure 15 The LCD monitor is widely used with desktop computers.
speakers
Introduction to Computers COM 11
Hard Disks
A hard disk is a storage device that contains one or more inflexible, circular platters that use magnetic particles to store data, instructions, and information. The system unit on most personal computers contains at least one hard disk, sometimes called an internal hard disk because it is not portable. Users store documents, spread- sheets, presentations, databases, e-mail messages, Web pages, digital photos, music, videos, and software on hard disks. Hard disks store data and instructions in tracks and sectors on a platter (Figure 17). A track is a narrow recording band that forms a full circle on the surface of the disk. The disk’s storage locations consist of pie-shaped sections, which break the tracks into small arcs called sectors. On a hard disk, a sector typically stores up to 512 bytes of data. Storage capacities of internal hard disks for personal computers range from 160 GB to more than 2 TB. On desktop computers, platters most often have a size of approximately 3.5 inches in diameter. On notebook computers and mobile devices, the diameter is 2.5 inches or less. A typical hard disk has multiple platters stacked on top of one another. Each platter has two read/write heads, one for each side. The hard disk has arms that move the read/write heads to the proper location on the platter (Figure 18). The hard disk platters spin at a high rate of speed, typically 5,400 to 15,000 revolutions per minute. On today’s computers, the plat- ters typically stop spinning or slow down after a specified time to save power. When reading or writing, the read/ write heads on a hard disk do not actually touch the surface of the disk. The distance between the read/write heads and the platters is about two millionths of one inch. This close clearance means that dirt, hair, dust, smoke, or other particles could cause the hard disk to have a head crash , when a read/write head touches a platter, usually resulting in loss of data or sometimes the entire disk. Although current hard disks are sealed tightly to keep out contaminants, head crashes do occur occasionally. Thus, it is crucial that you back up your hard disk regularly. A backup is a duplicate of a file, program, or disk placed on a separate storage medium that you can use in case the original is lost, damaged, or destroyed.
17 18 1 222222 16 15
14
13
12 (^11 10 9 )
7
6
5
4
3
Figure 17 Tracks form circles on the surface of a hard disk platter. The disk’s storage locations are divided into pie-shaped sections, which break the tracks into small arcs called sectors.
sectors
track
Figure 18 This figure shows how a hard disk works.
Step 3
When software requests a disk access, the read/write heads determine the current or new location of the data.
Step 2
A small motor spins the platters while the computer is running.
Step 1
The circuit board controls the movement of the head actuator and a small motor.
Step 4
The head actuator positions the read/write head arms over the correct location on the platters to read or write data.
How a Hard Disk Works
Introduction to Computers COM 13
A memory card is a removable flash memory device, usually no bigger than 1.5 inches in height or width, that you insert and remove from a slot in a computer, mobile device, or card reader/writer (Figure 22). Memory cards enable mobile users easily to transport digital photos, music, or files to and from mobile devices and computers or other devices.
digital camera
card reader
portable media player
photo printer
desktop computer
smart phone
Figure 22 Many types of computers and devices have slots for memory cards.
memory cards
COM 14 Introduction to Computers
Various Memory Cards
Media Type Storage Capacity Use CompactFlash (CF)
512 MB to 100 GB Digital cameras, smart phones, PDAs, photo printers, portable media players, notebook computers, desktop computers
Secure Digital (SD)
512 MB to 8 GB Digital cameras, digital video cameras, smart phones, PDAs, photo printers, portable media players
SDHC 4 to 32 GB Digital cameras
microSD
1 to 2 GB Smart phones, portable media players, handheld game consoles, handheld navigation devices
microSDHC
4 to 16 GB Smart phones, portable media players, handheld game consoles, handheld navigation devices
xD Picture Card 256 MB to 2 GB^ Digital cameras, photo printers
Memory Stick PRO Duo
1 to 16 GB Digital cameras, smart phones, handheld game consoles
Memory Stick Micro (M2)
1 to 16 GB Smart phones
Figure 23 A variety of memory cards.
Common types of memory cards include CompactFlash (CF), Secure Digital (SD), Secure Digital High Capacity (SDHC), microSD, microSDHC, xD Picture Card, Memory Stick PRO Duo, and Memory Stick Micro (M2) (Figure 23).
Many different formats of optical discs exist today. Figure 27 identifies a variety of optical disc formats and specifies whether a user can read from the disc, write on the disc, and/or erase the disc. A CD-ROM, or compact disc read-only memory, is a type of optical disc that users can read but not write (record) or erase — hence, the name read-only. Manufacturers write the contents of standard CD-ROMs. A standard CD-ROM is called a single-session disc because manufacturers write all items on the disc at one time. Software manufac- turers often distribute programs using CD-ROMs. A typical CD-ROM holds from 650 MB to 1 GB of data, instructions, and information. To read a CD-ROM, insert the disc in a CD-ROM drive or a CD-ROM player. Because audio CDs and CD-ROMs use the same laser technology, you may be able to use a CD-ROM drive to listen to an audio CD while using the computer. A CD-R (compact disc-recordable) is a multisession optical disc on which users can write, but not erase, their own items such as text, graph- ics, and audio. Multisession means you can write on part of the disc at one time and another part at a later time. Each part of a CD-R can be written on only one time, and the disc’s contents cannot be erased. A CD-RW (compact disc-rewritable) is an erasable multisession disc you can write on multiple times. To write on a CD-RW disc, you must have optical disc burning software and a CD-RW drive. Burning is the process of writing on an optical disc. A popular use of CD-RW and CD-R discs is to create audio CDs. For example, users can record their own music and save it on a CD, purchase and download songs from the Web to their computer and then burn the songs on a CD, or rearrange tracks on a purchased music CD. The process of copying audio and/or video data from a purchased disc and saving it on a storage medium is called ripping. Although CDs have large storage capacities, even a CD cannot hold many of today’s complex programs. Thus, some software companies have moved from CDs to the larger DVDs — a technology that can be used to store large amounts of text and even videos (Figure 28). A DVD-ROM (digital versatile disk-read-only memory or digital video disc-read-only memory) is a high-capacity optical disc on which users can read but not write or erase. Manufacturers write the contents of DVD-ROMs and distribute them to consumers. DVD-ROMs store movies, music, huge databases, and complex software. To read a DVD-ROM, you need a DVD-ROM drive or DVD player. Most DVD-ROM drives also can
Figure 27 Manufacturers sell CD-ROM, read audio CDs, CD-ROMs, CD-Rs, and CD-RWs. DVD-ROM, and BD-ROM media prerecorded (written) with audio, video, and software. Users cannot change the contents of these discs. Users, however, can purchase the other formats of optical discs as blank media and record (write) their own data, instructions, and information on these discs.
Optical Disc Formats
Optical Disc Read Write Erase CD-ROM
p CD-ROM (^) Y N N
CD-RCDCD Y Y N
CD-RWCD-CD Y Y Y
DVD- ROM BD-ROM
DVDV RO BD
Y N N
DVD-R DVD+R BD-R
Y Y N
DVD-RW DVD+RW DVD-RAM BD-RE
Y Y Y
BDBDD R
DV BD
DVD DVD drive
Figure 28 A DVD-ROM is a high-capacity optical disc.
CDs For more information, visit scsite.com/ic8/weblink and then click CDs.
COM 16 Introduction to Computers
Introduction to Computers COM 17
A newer, more expensive DVD format is Blu-ray, which is a higher capacity and better quality than standard DVDs, especially for high-definition audio and video. A Blu-ray Disc (BD) has storage capacities of 100 GB, with expectations of exceeding 200 GB in the future. Many types of recordable and rewritable DVD formats are available. DVD-R, DVD+R, and BD-R allow users to write on the disc once and read (play) it many times. DVD-RW, DVD+RW, and DVD+RAM are three competing rewritable DVD formats. Similarly, BD-RE is a high-capacity rewritable Blu-ray format. To write on these discs, you must have a compatible drive or recorder.
Cloud Storage
Cloud storage is an Internet service that provides hard disk storage to computer users (Figure 29). Fee arrangements vary. For example, one cloud storage service provides 25 GB of storage free to regis- tered users; another charges $5 per month for 150 GB of storage. For organizations, cloud storage services typically charge for storage on a per gigabyte basis, such as 15 cents per gigabyte. Types of services offered by cloud stor- age providers vary. Figure 30 identifies a variety of cloud storage providers. Figure 29 An example of one Web site advertising its storage service.
Communications Devices
A communications device is a hardware component that enables a computer to send (transmit) and receive data, instructions, and information to and from one or more computers or mobile devices. A widely used communications device is a modem (Figure 1 on page COM 2). Communications occur over transmission media such as cables, telephone lines, cellular radio networks, and satellites. Some transmission media, such as satellites and cellular radio networks, are wireless , which means they have no physical lines or wires. People around the world use computers and communications devices to communicate with each other using one or more transmission media.
DVDs For more information, visit scsite.com/ic8/weblink and then click DVDs.
Figure 30 Some of the more widely used cloud storage providers.
Cloud Storage Providers
Web Site Names Type of Storage Provided Box.net, IDrive, Windows Live SkyDrive Backup or additional storage for any type of file Flickr, Picasa Digital photos YouTube Digital videos Facebook, MySpace Digital photos, digital videos, messages, and personal information Google Docs Documents, spreadsheets, presentations Gmail, Windows Live Hotmail, Yahoo! Mail E-mail messages Amazon EC2, Amazon S3, Nirvanix Enterprise-level storage
Introduction to Computers COM 19
Presentation Presentation software is application software that allows users to create visual aids
for presentations to communicate ideas, messages, and other information to a group (Figure 33). The presentations can be viewed as slides, sometimes called a slide show, that are displayed on a large monitor or on a projection screen.
Figure 32 Word processing software is used to create letters, memos, newsletters, and other documents.
Figure 33 Presentation software allows the user to produce professional-looking presentations.
Word Processing Word processing software is used to create, edit, format, and print documents
(Figure 32). A key advantage of word processing software is that users easily can make changes in documents, such as correcting spelling; changing margins; and adding, deleting, or relocating words, sentences, or entire paragraphs.
Word Processing Software For more information, visit scsite.com/ic8/weblink and then click Word Processing Software.
Presentation Software For more information, visit scsite.com/ic8/weblink and then click Presentation Software.
COM 20 Introduction to Computers
Spreadsheet Spreadsheet software allows users to organize data in rows and columns and perform
calculations on the data (Figure 34). These rows and columns collectively are called a worksheet. Most spreadsheet software has basic features to help users create, edit, and format worksheets.
Figure 34 With spreadsheet software, you create worksheets that contain data arranged in rows and columns, and you can perform calculations on the data in the worksheets.
Spreadsheet Software For more information, visit scsite.com/ic8/weblink and then click Spreadsheet Software.
Database A database is a collection of data organized in a manner that allows access, retrieval,
and use of that data. Database software is application software that allows users to create, access, and manage a database (Figure 35). Using database software, you can add, change, and delete data in a database; sort and retrieve data from the database; and create forms and reports using the data in the database.
Figure 35 Database software allows the user to enter, retrieve, and update data in an organized and efficient manner.
Database Software For more information, visit scsite.com/ic8/weblink and then click Database Software.
