Introduction to Computers Fall 2005

Computers in Your Life 

Most skill-based jobs heavily depend on the creation, collection, and dissemination of information.

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Computers are also prevalent in the home, as well as in our society in general.

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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

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Processing—the conversion of input to output

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Output—the results of computer processing

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Storage—saving data, results, or programs for future use 3

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Traditional and Multimedia Hardware 

A computer system consists of the computer itself and its peripheral equipment.

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Multimedia computer systems contain special hardware for use with sound and video.

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The CPU is at the heart of any computer system.

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Volatile memory temporarily stores programs and input while they are being processed.

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Software 

The programs or instructions used to tell the computer hardware what to do.

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Application software performs specific tasks or applications.

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Systems software allows a computer to operate and run application software. 7

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Data, Information, and Programs 

Data = raw, unorganized facts 

Can be in the form of text, graphics, audio, or video

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Information = data that has been processed into a useful form

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Programs = instructions that tell the computer how to process data to produce the results you want

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Users and Computer Professionals 

Users, or end users, are the people in the computing environment who need the output that computer systems produce.

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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.

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The Internet 

The Internet is the largest and most well known computer network in the world.

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Individuals connect using an ISP.

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E-mail and accessing the Web are two of the most common Internet activities.

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Accessing Networks 

Modem or other network adapter

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Appropriate software program

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ISP

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User ID to log on

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Web browser

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Network Servers 

Network servers manage resources on a network.

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Web servers are servers connected to the Internet to store Web pages.

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Online = when a computer can send or receive data from a computer network. 15

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Computer Systems to Fit Every Need 

Microcomputers

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Midrange computers

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Mainframe computers

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Supercomputers

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Mobile Devices 

Very small computing devices

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Based on a wireless phone or pager

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Limited Internet access

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Personal Computers 

Microprocessors allow for the creation of computers small enough to fit on a desk or lap. 

Desktop units

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Portable units

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Personal Computers, cont’d. 

PCs designed for just network use are referred to as network computers or thin clients.

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PCs or devices designed just for Internet access are called Internet appliances.

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Personal Computers, cont’d. 

PC compatible—a personal computer based on Intel microcomputer or compatible CPUs

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Macintosh—a type of personal computer manufactured by Apple

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Midrange Computers 

Medium-sized computers

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Fall between microcomputers and mainframes in processing power

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Mainframes 

Mainstay of almost all large organizations

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Specialize in high-volume processing of business transactions

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Supercomputers 

Used in organizations that have extraordinary demands for processing power

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Offer very fast speeds and extreme degrees of accuracy

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Computers and Society 

The information age = the prominence of information technology.

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Benefits of a computer-oriented society include the fact that day-to-day operations of many individuals are positively affected by computers.

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Problems include health and privacy concerns.

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Starting Your Computer: The Boot Process 

User turns on the power to the PC and monitor.

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PC’s operating system is then loaded into memory.

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Appropriate desktop or other user interface will be displayed.

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Using the Windows Operating System 

Microsoft Windows uses a graphical user interface (GUI)

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WYSIWIG = What You See Is What You Get

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Recent versions: Windows 95, Windows 98, Windows 2000, Windows Me, Windows XP 28

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The Windows Interface 

Desktop

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Windows

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Menus

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Icons

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Dialog boxes 30

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Opening Windows and Starting Programs 

Click a taskbar toolbar button.

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Click a desktop icon if it looks like a hyperlink.

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Double-click a desktop icon if it doesn’t look like a hyperlink.

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Click the Start button and then select the desired program from the Start menu.

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Manipulating Windows 

Active window

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Minimizing and maximizing windows

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Resizing and moving windows

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Scroll bars

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Shutting Down the Computer 

Standby mode reduces power consumption.

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The computer should always be shut down through the Start menu.

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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.

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Using the Internet and World Wide Web 

The Internet is a worldwide collection of networks connecting millions of computers all over the world.

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The World Wide Web is the collection of Web pages accessed through the Internet.

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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.

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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.

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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

Internet Addresses 

An Internet address tells where something on the Internet can be located.

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IP addresses and domain names identify computers available through the Internet.

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E-mail addresses identify a person on the Internet.

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Internet Addresses, cont’d.

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Surfing the Web 

Use hyperlinks, the address bar or location bar, or the Back and Forward toolbar buttons to surf the Web.

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Things that you may encounter on a Web page:

text and images e-mail hyperlinks form fields 

frames animation multimedia links 

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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. 

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Searching the Web 

A search site typically uses a search engine in conjunction with a huge directory of Web pages to retrieve information.

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Keyword search: keywords are typed into a search box and then hyperlinks for matching Web pages are displayed.

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Directory search: a series of increasingly specific categories are selected until links for matching Web pages are displayed.

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E-Mail 

One of the first applications to appear on the Internet and still the most popular.

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An e-mail message can be sent to anyone with an Internet e-mail address.

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Browser-based e-mail remains on the e-mail provider’s computer until it is requested.

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Sending E-Mail 

E-mail can be sent over private networks, over the Internet, or over some combination of the two.

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E-mail hyperlinks on Web pages can be used to start an e-mail message using your e-mail program.

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Many e-mail programs also enable users to attach files.

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Receiving E-Mail 

E-mail can be received over private networks, over the Internet, or over some combination of the two.

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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

Managing E-Mail 

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.

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Create additional folders to organize e-mail you would like to keep.

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Delete unneeded e-mail messages periodically and then empty the Trash folder to free up space on your hard drive.

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Mailing Lists, Newsgroups, Chat, and Instant Messaging 

Mailing lists: topical discussion groups that use e-mail to communicate.

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Newsgroups: targeted to specific topics; are grouped and organized by thread before they are made available to users.

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Mailing Lists, Newsgroups, Chat, and Instant Messaging, cont’d. 

Chat enables people to engage in interactive conversations over the Internet.

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Instant messaging lets you set up a buddy list and notifies you when those individuals are online.

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Downloading and Installing Plug-Ins and Other Files 

Downloading a file means to copy a file over the Internet to your PC.

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A browser plug-in program adds new capabilities to your browser.

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Downloading Files 

Click the appropriate link and specify where the file should be stored on your PC.

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Sometimes files may be opened automatically in your browser if you have the appropriate plug-in.

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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.) 

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Digital Data Representation 

Computers today are mostly digital computers—devices that can only understand two states.

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The two states of a digital computer are typically represented by 0s and 1s.

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Natural-language messages are translated to the computer into binary form. 55

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The Binary Numbering System 

The binary numbering system represents all numbers using just two symbols (0 and 1).

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Coding Systems for Text-Based Data 

ASCII and EBCDIC 

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Fixed-length codes that can represent any single character of data as a string of eight bits

Unicode 

A 16-bit code that can be used to represent textbased data in virtually any written language

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Byte Terminology 

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

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Machine Language 

Machine language is the binary-based code used to represent program instructions.

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The basic set of machine-language instructions that a CPU can understand is that CPU’s instruction set.

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Most programmers rely on language translators to translate their programs into machine language for them.

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Inside the System Unit 

The system unit of a PC is the case that houses processing hardware and other hardware.

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All of the hardware contained within the system unit is connected to the system board or motherboard.

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CPU 

The microprocessor (CPU chip) contains a variety of circuitry and components and is connected to the motherboard.

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CPU, cont’d. 

Processing speed is measured in megahertz (MHz) or gigahertz (GHz).

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A computer word is a group of bits or bytes that may be manipulated and stored as a unit.

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Other factors that affect the speed of the computer include RAM, cache memory, bus width, and bus speed.

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Memory: RAM 

RAM is volatile

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Types of RAM

DRAM SRAM SDRAM DDR SDRAM RDRAM PC133 SRAM 65

Memory 

Cache memory

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Registers

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ROM

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Flash memory 66

Buses 

Buses are electronic paths that data travels around on a computer system.

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Internal buses move data around within the CPU.

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Expansion buses establish links with peripheral devices. 67

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System Expansion 

Expansion cards for desktop PCs 

Video-graphics board, fax/modem board, or sound card

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PC cards: expansion for notebook & other portables

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Expansion for handhelds and mobile devices 

USB port, SD cards, MM cards, and Springboard modules

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Ports 

Common ports:

Serial

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Parallel

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SCSI

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USB

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Firewire Network MIDI IrDA

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Typical CPU Components 

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Arithmetic/logic unit

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Decode unit

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Prefetch unit

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Internal cache

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Bus interface unit

Control unit Registers

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The System Clock and the Machine Cycle 

The system clock ticks on a regular basis to help synchronize the computer’s components.

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The machine cycle is the series of operations involved in the execution of a single, machinelevel instruction.  

Instruction stage Execution stage

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Properties of Storage Systems: Removable vs. Fixed Media 

Fixed media: typically faster and less expensive

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Removable media: unlimited capacity and can be easily transported and secured

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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)

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Direct access (random access): records can be retrieved in any sequence, independent of physical storage (most disks and optical media)

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Properties of Storage Systems: Logical vs. Physical Representation 

Logical file representation refers to the user’s view of the way data is stored.

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Physical file representation is the actual physical way the data is stored on the storage media as viewed by the computer.

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Magnetic Disk Systems 

Magnetic disks are the most important storage medium in computers today.

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Two popular types:  

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floppy disks hard disks

Data is written by magnetizing particles on the disks in a certain way to represent 1s and 0s.

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Floppy Disks 

Physical properties 

Most are 3½ inches in diameter and hold 1.44 megabytes.

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Floppy Disks, cont’d. 

Tracks, sectors, and clusters 

The disk’s file directory keeps track of the contents of the disk.

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Floppy Disks, cont’d. 

Using floppy disks 

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Must be inserted into the proper drive in the proper direction Should not be removed when the disk is being accessed

Superdiskettes 

Zip drives, SuperDisk drives, HiFD drives

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Hard Disks 

Physical properties 

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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

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Hard Disks, cont’d. 

Reading and writing data 

Obstacles on a hard-disk system can damage the surface and read/write head.

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Hard Disks, cont’d. 

Disk access time 

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Disk cache 

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Factors: seek time, rotational delay, data movement time

Strategy for speeding up system performance

Disk standards 

ATA/IDE and SCSI, Fibre Channel

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Hard Disks, cont’d.

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Removable hard disk systems 

Offer large storage capacities and portability

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Hard Disks, cont’d. 

Hard disk systems for notebooks 

Can use either internal or removable hard drives

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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

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Optical Discs 

Laser beams write and read data packed at very tight storage densities, several times finer than that of a typical magnetic disk.

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CDs 

CDs are permanently etched when data is stored on the disc.

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Recordable (CD-R) discs can be written to, but not erased and rewritten.

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Rewritable (CD-RW) CDs can be used in the same way as magnetic disks—data can be stored and erased as needed.

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DVDs 

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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.

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Magneto-Optical Discs 

M-O discs use a combination of magnetic and optical technologies.

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Can store up to 5.2 GB per disc.

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Magnetic Tape Systems 

Magnetic tape is used primarily for backup purposes.

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The device that reads tapes is called a tape drive.

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Most tape media are in the form of cartridge tapes, though detachable-reel tapes exist as well.   98

Online Storage 

Online storage is usually storage on a server accessible over the Internet or another network.

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Online storage can be used as a primary storage medium or for backup or distribution purposes.

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Smart Cards 

Smart card: credit-card-sized piece of plastic that contains some type of computer circuitry.  

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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.

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Flash Memory Devices 

Flash memory sticks 

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Flash memory cards 

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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

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Comparing Storage Alternatives

Speed, expense, portability, and compatibility

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Most PC users require   

Hard drive CD or DVD drive Floppy drive 103