Introduction to Computers Fall 2005
Computers in Your Life
Most skill-based jobs heavily depend on the creation, collection, and dissemination of information.
Computers are also prevalent in the home, as well as in our society in general.
Having experience with, and a basic level of comfort with, computers is important for everyone. 2
What Is a Computer and What Does It Do?
Input—what is supplied to a computer to process
Processing—the conversion of input to output
Output—the results of computer processing
Storage—saving data, results, or programs for future use 3
Traditional and Multimedia Hardware
A computer system consists of the computer itself and its peripheral equipment.
Multimedia computer systems contain special hardware for use with sound and video.
The CPU is at the heart of any computer system.
Volatile memory temporarily stores programs and input while they are being processed.
The programs or instructions used to tell the computer hardware what to do.
Application software performs specific tasks or applications.
Systems software allows a computer to operate and run application software. 7
Data, Information, and Programs
Data = raw, unorganized facts
Can be in the form of text, graphics, audio, or video
Information = data that has been processed into a useful form
Programs = instructions that tell the computer how to process data to produce the results you want
Users and Computer Professionals
Users, or end users, are the people in the computing environment who need the output that computer systems produce.
Programmers are the people whose job it is to write programs to supply this information. 11
Computer Networks and the Internet
A computer network ties users together to share hardware, software, and data, as well as to electronically communicate with each other.
The Internet is the largest and most well known computer network in the world.
Individuals connect using an ISP.
E-mail and accessing the Web are two of the most common Internet activities.
Modem or other network adapter
Appropriate software program
User ID to log on
Network servers manage resources on a network.
Web servers are servers connected to the Internet to store Web pages.
Online = when a computer can send or receive data from a computer network. 15
Computer Systems to Fit Every Need
Very small computing devices
Based on a wireless phone or pager
Limited Internet access
Microprocessors allow for the creation of computers small enough to fit on a desk or lap.
Personal Computers, cont’d.
PCs designed for just network use are referred to as network computers or thin clients.
PCs or devices designed just for Internet access are called Internet appliances.
Personal Computers, cont’d.
PC compatible—a personal computer based on Intel microcomputer or compatible CPUs
Macintosh—a type of personal computer manufactured by Apple
Fall between microcomputers and mainframes in processing power
Mainstay of almost all large organizations
Specialize in high-volume processing of business transactions
Used in organizations that have extraordinary demands for processing power
Offer very fast speeds and extreme degrees of accuracy
Computers and Society
The information age = the prominence of information technology.
Benefits of a computer-oriented society include the fact that day-to-day operations of many individuals are positively affected by computers.
Problems include health and privacy concerns.
Starting Your Computer: The Boot Process
User turns on the power to the PC and monitor.
PC’s operating system is then loaded into memory.
Appropriate desktop or other user interface will be displayed.
Using the Windows Operating System
Microsoft Windows uses a graphical user interface (GUI)
WYSIWIG = What You See Is What You Get
Recent versions: Windows 95, Windows 98, Windows 2000, Windows Me, Windows XP 28
The Windows Interface
Dialog boxes 30
Opening Windows and Starting Programs
Click a taskbar toolbar button.
Click a desktop icon if it looks like a hyperlink.
Double-click a desktop icon if it doesn’t look like a hyperlink.
Click the Start button and then select the desired program from the Start menu.
Minimizing and maximizing windows
Resizing and moving windows
Shutting Down the Computer
Standby mode reduces power consumption.
The computer should always be shut down through the Start menu.
The Shut Down dialog box can also be used to log off a network so another user may log on, as well as to restart the computer.
Using the Internet and World Wide Web
The Internet is a worldwide collection of networks connecting millions of computers all over the world.
The World Wide Web is the collection of Web pages accessed through the Internet.
Computers that host Web pages are called Web servers. 36
What Is a Browser?
A Web browser is a program used to view Web pages.
Common browsers Microsoft Internet Explorer Netscape Navigator MSN Explorer Opera America Online 37
Accessing the Internet
You can be connected via a direct or always-on connection, or a dial-up connection.
Internet service providers (ISPs) are the gateway to the Internet.
Typically charge monthly fees Most allow you to use the Web browser of your choice 38
An Internet address tells where something on the Internet can be located.
IP addresses and domain names identify computers available through the Internet.
E-mail addresses identify a person on the Internet.
Internet Addresses, cont’d.
Surfing the Web
Use hyperlinks, the address bar or location bar, or the Back and Forward toolbar buttons to surf the Web.
Things that you may encounter on a Web page:
text and images e-mail hyperlinks form fields
frames animation multimedia links
Using Bookmarks and the History List Visited Web pages are recorded in the browser’s history list. To save Web page URLs on a more permanent basis, bookmarks or favorites are used.
Searching the Web
A search site typically uses a search engine in conjunction with a huge directory of Web pages to retrieve information.
Keyword search: keywords are typed into a search box and then hyperlinks for matching Web pages are displayed.
Directory search: a series of increasingly specific categories are selected until links for matching Web pages are displayed.
One of the first applications to appear on the Internet and still the most popular.
An e-mail message can be sent to anyone with an Internet e-mail address.
Browser-based e-mail remains on the e-mail provider’s computer until it is requested.
E-mail can be sent over private networks, over the Internet, or over some combination of the two.
E-mail hyperlinks on Web pages can be used to start an e-mail message using your e-mail program.
Many e-mail programs also enable users to attach files.
E-mail can be received over private networks, over the Internet, or over some combination of the two.
E-mail is often sent using a browser’s built-in e-mail program, such as Microsoft Outlook, Microsoft Outlook Express, or Netscape Mail. 47
Sent and received messages are stored in separate folders, and deleted e-mail messages are moved to some type of Trash or Deleted Items folder.
Create additional folders to organize e-mail you would like to keep.
Delete unneeded e-mail messages periodically and then empty the Trash folder to free up space on your hard drive.
Mailing Lists, Newsgroups, Chat, and Instant Messaging
Mailing lists: topical discussion groups that use e-mail to communicate.
Newsgroups: targeted to specific topics; are grouped and organized by thread before they are made available to users.
Mailing Lists, Newsgroups, Chat, and Instant Messaging, cont’d.
Chat enables people to engage in interactive conversations over the Internet.
Instant messaging lets you set up a buddy list and notifies you when those individuals are online.
Downloading and Installing Plug-Ins and Other Files
Downloading a file means to copy a file over the Internet to your PC.
A browser plug-in program adds new capabilities to your browser.
Click the appropriate link and specify where the file should be stored on your PC.
Sometimes files may be opened automatically in your browser if you have the appropriate plug-in.
The amount of time required to download a file depends on the size of the file and the speed of your Internet connection. 53
Using Downloaded Files Possible file types: Zipped (.zip) PDF (.pdf) Image (.gif, .jpg, .tif, .bmp, etc.) Music (.wav, .mp3, etc.)
Video (.avi, .mov, etc.) Executable (.exe) Application (.doc, .xls, etc.)
Digital Data Representation
Computers today are mostly digital computers—devices that can only understand two states.
The two states of a digital computer are typically represented by 0s and 1s.
Natural-language messages are translated to the computer into binary form. 55
The Binary Numbering System
The binary numbering system represents all numbers using just two symbols (0 and 1).
Coding Systems for Text-Based Data
ASCII and EBCDIC
Fixed-length codes that can represent any single character of data as a string of eight bits
A 16-bit code that can be used to represent textbased data in virtually any written language
Byte - a string of eight bits kilobytes (KB) thousands of bytes megabytes (MB) millions of bytes gigabytes (GB) billions of bytes terabytes (TB) trillions of bytes petabyte (PB) about 1 quadrillion bytes exabyte (EB) about 1 quintillion bytes
Machine language is the binary-based code used to represent program instructions.
The basic set of machine-language instructions that a CPU can understand is that CPU’s instruction set.
Most programmers rely on language translators to translate their programs into machine language for them.
Inside the System Unit
The system unit of a PC is the case that houses processing hardware and other hardware.
All of the hardware contained within the system unit is connected to the system board or motherboard.
The microprocessor (CPU chip) contains a variety of circuitry and components and is connected to the motherboard.
Processing speed is measured in megahertz (MHz) or gigahertz (GHz).
A computer word is a group of bits or bytes that may be manipulated and stored as a unit.
Other factors that affect the speed of the computer include RAM, cache memory, bus width, and bus speed.
RAM is volatile
Types of RAM
DRAM SRAM SDRAM DDR SDRAM RDRAM PC133 SRAM 65
Flash memory 66
Buses are electronic paths that data travels around on a computer system.
Internal buses move data around within the CPU.
Expansion buses establish links with peripheral devices. 67
Expansion cards for desktop PCs
Video-graphics board, fax/modem board, or sound card
PC cards: expansion for notebook & other portables
Expansion for handhelds and mobile devices
USB port, SD cards, MM cards, and Springboard modules
Firewire Network MIDI IrDA
Typical CPU Components
Bus interface unit
Control unit Registers
The System Clock and the Machine Cycle
The system clock ticks on a regular basis to help synchronize the computer’s components.
The machine cycle is the series of operations involved in the execution of a single, machinelevel instruction.
Instruction stage Execution stage
Properties of Storage Systems: Removable vs. Fixed Media
Fixed media: typically faster and less expensive
Removable media: unlimited capacity and can be easily transported and secured
Properties of Storage Systems: Random vs. Sequential Access
Sequential access: records in a file can be retrieved only in the same sequence in which they are physically stored (like tape)
Direct access (random access): records can be retrieved in any sequence, independent of physical storage (most disks and optical media)
Properties of Storage Systems: Logical vs. Physical Representation
Logical file representation refers to the user’s view of the way data is stored.
Physical file representation is the actual physical way the data is stored on the storage media as viewed by the computer.
Magnetic Disk Systems
Magnetic disks are the most important storage medium in computers today.
Two popular types:
floppy disks hard disks
Data is written by magnetizing particles on the disks in a certain way to represent 1s and 0s.
Most are 3½ inches in diameter and hold 1.44 megabytes.
Floppy Disks, cont’d.
Tracks, sectors, and clusters
The disk’s file directory keeps track of the contents of the disk.
Floppy Disks, cont’d.
Using floppy disks
Must be inserted into the proper drive in the proper direction Should not be removed when the disk is being accessed
Zip drives, SuperDisk drives, HiFD drives
Permanently sealed inside the hard drive— allows faster speeds than removable systems
Hard disk addressing
Disk cylinder—the collection of tracks located in the same location on a set of hard disk surfaces
Hard Disks, cont’d.
Reading and writing data
Obstacles on a hard-disk system can damage the surface and read/write head.
Hard Disks, cont’d.
Disk access time
Factors: seek time, rotational delay, data movement time
Strategy for speeding up system performance
ATA/IDE and SCSI, Fibre Channel
Hard Disks, cont’d.
Removable hard disk systems
Offer large storage capacities and portability
Hard Disks, cont’d.
Hard disk systems for notebooks
Can use either internal or removable hard drives
Hard Disks, cont’d.
Hard disk systems for large computer systems
May use a system consisting of multiple hard drives; RAID is a recent trend
Laser beams write and read data packed at very tight storage densities, several times finer than that of a typical magnetic disk.
CDs are permanently etched when data is stored on the disc.
Recordable (CD-R) discs can be written to, but not erased and rewritten.
Rewritable (CD-RW) CDs can be used in the same way as magnetic disks—data can be stored and erased as needed.
DVDs are read-only and may replace VHS as the movie media of choice. Rewritable DVDs (DVD-RAM or DVD+RW) allow users to record on DVD discs.
M-O discs use a combination of magnetic and optical technologies.
Can store up to 5.2 GB per disc.
Magnetic Tape Systems
Magnetic tape is used primarily for backup purposes.
The device that reads tapes is called a tape drive.
Most tape media are in the form of cartridge tapes, though detachable-reel tapes exist as well. 98
Online storage is usually storage on a server accessible over the Internet or another network.
Online storage can be used as a primary storage medium or for backup or distribution purposes.
Smart card: credit-card-sized piece of plastic that contains some type of computer circuitry.
Holds less than a few megabytes Commonly used to store prepaid amounts of digital cash, or personal information
Smart card readers are attached to a PC or built into a cell phone, keyboard, or other device.
Flash Memory Devices
Flash memory sticks
Flash memory cards
Size of a stick of gum; hold from 4 to 64 MB each Standards include CompactFlash, SmartMedia, Secure Digital (SD), and MultiMedia Card (MMC)
Flash memory drives
Have no moving parts—are more shock-proof and portable than conventional drives
Comparing Storage Alternatives
Speed, expense, portability, and compatibility
Most PC users require
Hard drive CD or DVD drive Floppy drive 103