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154 Cards in this Set
- Front
- Back
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Twisted-Pair Wire
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Two strands of insulated copper wire, twisted around each other
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Twisted-Pair Wire-disadvantage
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relatively slow (1-128 Mbps), interference
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Coaxial Cable
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Insulated copper wire wrapped in a solid or braided metal shield, then an external cover
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Advantages of Coaxial Cable
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less interference, faster (~200 Mbps)
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Fiber-Optic Cable
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Dozens or hundreds of thin strands of glass or plastic that transmit pulsing beams of light rather than electricity
-The light used is typically IR |
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Fiber-Optic Cable
Advantages |
-fast (~ 2Gbps), less interference, more reliable, lighter, cannot be easily wiretapped
-Dispersion considerations, alleviated by repeaters and optical amplifiers (1987) |
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Infrared Transmission (IR)
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Transmission speeds of 1-4 Mbps, deprecated technology for wireless mice and keyboards
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Broadcast Radio
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For long range communications
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Microwave Radio
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Super-high frequency radio waves (~ 45 Mbps)
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Communication Satellites
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-Microwave relay stations that orbit around the earth
-Eliminate the line-of -sight limitation of the above technologies |
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GEO
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(22K mi from earth): e.g. broadcast TV, weather, surveillance
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MEO
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(5K-10K mi from earth): e.g. navigation and communication satellites such as U.S. NAVSTAR and GPS
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LEO
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(200-1000 mi from earth): e.g. surveillance, imaging
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Bluetooth
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A wireless standard aimed at linking cell phones, PDAs, computers, and peripheral devices up to 30 ft, speeds < 1 Mbps
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WiFi (Wireless Fidelity)
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-A wireless standard aimed at helping portable computers and handheld devices to communicate at high speeds and share Internet connections at distances up to 300 ft
-Uses WAP, 10 x speed of Bluetooth -WiFi utilizes WEP, WPA & WPA2 -Auto-connection concerns |
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Modems
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Modems are devices that convert signals between analog and digital formats to allow for proper transmission of data over different physical mediums
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types of modems
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Internal & External
Wireless Cable DSL Power lin |
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Packet:
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A fixed-length block of data for transmission. Includes headers, src & dest addresses, and a payload. Data transmissions are broken up into packets.
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Bandwidth
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The range or band of frequencies that a transmission medium can carry in a given period of time. Can be expressed in Hz or bps.
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Bandwidth
Baseband |
Only one signal can travel at a time
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Bandwidth
Broadband |
Several signals can be sent at once
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The OSI Model
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A seven-layer logical break-down of network interaction to facilitate communication standards
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Protocol
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A set of conventions that govern the format of data transmitted electronically. They ensure that all data is exchanged in a consistent format
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TCP/IP
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-The protocols that enable all computers to interpret and use data transmitted over the Internet.
-TCP is a transport layer protocol and IP is a network layer protocol -TCP is reliable, in order, implements flow control |
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IP Address
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-Used to uniquely identify computers on the Internet
-Can be dynamic (changes for each session) or static (fixed) -Syntax: four sets of numbers between 0 and 255 separated by decimals (for IPv4), e.g. 196.129.1.6 -Dynamic IP addresses are assigned by DHCP servers -Dynamic addresses are suitable for clients, static addresses are suitable for persistent sites |
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Dial-up
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Cheap (< $20), slow (< 56 Kbps), widespread availability
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The “last mile” problem (Dial up)
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replacing copper wire lines is a financial and technical challenge
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T-Carrier (T1/T2/T3):
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A traditional trunk line that carries multiple telephone circuits
Speeds of up to 45 Mbps Cost: > $1,000 |
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Digital Subscriber Line (DSL)
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Principal competition to cable, always on
Speeds of 1.5-9 Mbps for downloads and 64 Kbps-1.5Mbps for uploads Availability limitations Cost: ~ $40 |
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Cable:
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Connects PCs to cable TV systems utilizing unused portions of cable for data transfer, always on
Speeds of 50 Mbps for downloads and 1.4 Mbps for uploads Performance issues Cost: ~ $40 |
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Satellite
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Communications satellites transmit microwaves from earth-based stations, always on
Speeds of 256-400 Kbps Cost: ~ $100 |
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Broadband over Power Lines (BPL):
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Uses existing electricity networks for data and voice transmission
Has potential for interference with radio signals Cost: ~ $30 |
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WiFi
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Wi-Fi permits transmission speeds of 1-11 Mbps, 300 ft range
Is it legal and technically safe to use the unsecured wireless connection to which you do not subscribe? |
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The Internet Hierarchy
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ISP (Internet Service Provider)
POP (Point Of Presence) NAP (Network Access Point)/ PNAP (Private/Peer NAP) Backbone |
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Internet 2
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Cooperative university/business research project
New standards for large-scale higher-speed data transmission Requires state-of-the-art infrastructure |
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Cell Phones
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Analog (1G), Digital (2G), Broadband (3G)
2G: U.S. wireless standards (GSM, TDMA, CDMA, FDMA) 2.5G: GPRS, EDGE 3G: EV-DO, UMTS |
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WiMAX
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Potential range: 30mi
Data transfer rates ranging from 15 Mbps to 40 Mbps |
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Mobile Security Concerns
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SMS spoofing (some use legitimate software such as Clickatell, Verizon blocks about 50,000 spam SMS per day)
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Mobile Security Concerns
Malicious code attacks |
Spread through Bluetooth, required restarting phone after exposure and user opening malicious file
Actions: dialers, delete files, draining batteries |
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Components of Networks
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Connection systems, computers with NICs, Network OS, Shared devices,
Routers (direct messages between different networks)/Hubs/Switches/Bridges (connect similar networks)/Gateways (connect dissimilar networks) |
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Types of Networks (based on coverage scope)
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WAN, MAN, LAN, etc
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Types of LANs (based on computer roles)
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Client/Server, P2P
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Network Topologies
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Bus (susceptible to collisions)
Ring Star (hub at the center, no collisions) |
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Machine Language
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Instructions written in binary
Programmer has to remember which combination of binary digits means what Each instruction performs one very-low level task Tedious, time-consuming and prone to errors Each CPU has its own machine language, i.e. machine language is machine-dependent Every program that is to run on a computer must be converted to machine language A subset of Pep/7 instructions |
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Assembly Language
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Uses mnemonic codes to represent machine language instructions
More user-friendly Assembly language is machine-dependent An assembler can be used to translate assembly language into machine language |
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High-Level Languages
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More similar to a human language
Allows programmers to write in a familiar notation General purpose, i.e. can be used to write programs that address a wide variety of problems High-level languages are machine-independent |
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compiler
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can convert an entire program of a high-level language into machine language before the program is executed
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source code
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The high-level version of the program
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object code or binary code
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The machine language version of the program
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interpreter
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translates each high-level program statement into machine language and executes it immediately, statement by statement
An interpreter does not save an object code version of the program |
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Very High-Level Languages
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Very high-level programming languages are problem-oriented
They are designed to solve specific problems Examples: report generators, query languages, etc. |
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Very High-Level Languages
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Very high-level programming languages are problem-oriented
They are designed to solve specific problems Examples: report generators, query languages, etc. |
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Object-Oriented Programming
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An Object is a self-contained module that can contain both data and procedures (methods) which read or manipulate the data.
An object can represent a person, an event, an action, etc. Objects are reusable Program creation becomes faster due to the reuse of objects |
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Encapsulation(opp)
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An object contains (encapsulates) both data and methods
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Inheritance(opp)
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Once you have created an object, you can use it as the foundation for similar objects that have the same behavior and characteristics
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Polymorphism(OPP)
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A procedure leads to different results depending on the object that it applies to
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Scripting Languages
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A script is a short list of self-executing commands
Can perform instructions without user-involvement or may be initiated by user-input |
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Variables
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Represent named places into which values are stored and from which values are retrieved
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Data types
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Integers
Floating point numbers Booleans Strings |
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Integers
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whole numbers
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Floating point numbers
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numbers with decimals
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Booleans
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true/false values
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Strings
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sequence of characters
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Variable names & naming conventions
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Variable names are case-sensitive
Cannot start with a number Cannot be a reserved keyword |
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Declaration
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A statement that associates an identifier with a variable
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Assignment
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Storing a value into a variable
Can be made via user input, fixed assignment, or using an expression |
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System Software
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enables application software to interact with the computer and manages the computer’s resources
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Operating System (OS
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The principal component of system software, manages basic operations of the computer
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Device Driver
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Helps the computer control peripheral devices
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Utility Program
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Supports, enhances, and expands capabilities of existing programs
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Language Translator
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Translates high-level language programs to machine code
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Backup
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Makes a duplicate copy of the specified data
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Data-Recovery
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Restores data that has been physically damaged or corrupted
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Virus Protection
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Scans files, detects, and removes viruses
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Data Compression
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Removes redundant elements, gaps, and unnecessary data from files
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Disk Scanner & Cleanup
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Detects and removes unnecessary files, detects and corrects disk problems
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Defragmenter
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Finds all scattered files on a hard disk and reorganizes them as contiguous files
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The Operating System
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The operating system (OS) is the principal component of system software
It consists of the master system of programs that manage the basic operations of the computer |
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Some of the functions of the OS are:
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Memory management
CPU scheduling Process management File management Security management |
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Software Platform
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A particular operating system on which a computer is based
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Disk Operating System (DOS):
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The original OS by Microsoft, command-driven user interface
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Network Operating Systems
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Netware, Linux, Unix, etc.
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Booting
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is the process of loading the OS into the computer’s main memory
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The Boot Disk
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A CD that contains all the files needed to launch the OS
When the computer is turned on with the boot disk in the disc drive, the OS files are forced to the BIOS, i.e. it takes precedence over obtaining the OS files from the hard drive |
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The process states:
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New
Ready Running Waiting Terminated |
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Non-preemptive Scheduling
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Scheduling that occurs when the currently executing process gives up the CPU voluntarily
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Preemptive Scheduling
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Scheduling that occurs when the OS decides to favor another process, preempting the currently executing process
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Turnaround Time
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The scheduling metric that measures the elapsed time between a process’ arrival in the ready state and its completion
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Approaches to CPU scheduling
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First-come first-serve (FCFS)
Shortest job next (SJN) Round robin |
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logical address
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is a value that specifies a generic location relative to the program but not with respect to the actual main memory device
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physical address
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is an actual address in the main memory device
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Address binding
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The mapping from a logical address to a physical address
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Three memory management techniques
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Single contiguous memory management
Partition memory management Paged memory management |
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Single Contiguous Memory Management
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The approach to memory management in which a program is loaded into one continuous area of memory
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Fixed Partition Technique
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The memory is divided into a specific number of partitions into which programs are loaded
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Dynamic Partition Technique
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The memory is divided into partitions as needed to accommodate programs
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Partition selection:
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First fit
Best fit Worst fit |
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Paged Memory Technique
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An approach in which process are divided into fixed-size pages and stored in memory frames when loaded
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Frame
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A fixed-size portion of main memory that holds a process page
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Page
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A fixed-size portion of a process that is stored in a memory frame
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Page-Map Table (PMT):
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The table used to keep track of page/frame relationships
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Vacuum Tubes
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Light-bulb sized electronic tubes with glowing filaments, high failure rates, damaged tubes had to be replaced for the computer to function
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Transistor:
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Developed in 1947 by Bell Labs, tiny electrically operated switch, alternate between “on” and “off” states
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Integrated Circuit
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An entire electronic circuit formed on a single “chip” often made of silicon
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Microchips
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AKA “industrial rice” Store and process data, has millions of micro-miniature electronic circuits etched on the chip via the photolithography process
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Processor Basics
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Vacuum Tubes
Transistor Integrated Circuit Microchips |
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Microprocessors
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CISC
RISC |
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RISC
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Used mostly in workstations, many seldom-used instructions are eliminated
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CISC
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Supports a large number of instructions at relatively low speeds
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Types of microprocessors used in most PCs
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Intel-Type
Motorola-Type PowerPC Type |
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Intel-Type
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Chips made by Intel, AMD, Cyrix, and others, used in 90% of computers, Intel on Mac
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Motorola-Type
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Chips made by Motorola and until recently was the only type exclusively used in Apple Macintosh PCs
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PowerPC Type
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Used by PowerMac and G5 Macintoshes
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Chipset
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Collection of interconnected chips that determine what type of processors, memory, and other hardware will work on the same motherboard
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Word Size
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The number of bits a processor may process at one time, typically 32 or 64
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The CPU consists of
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The Control Unit
ALU Registers Buses |
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The Control Unit
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directs electronic signals
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ALU
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Performs arithmetic and logical operations
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Registers
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Special high-speed storage areas that temporarily store data
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Buses
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Electrical data roadways through which bits are transmitted
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The machine cycle consists of four operations
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fetching, decoding, executing, storing results
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System Clock
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Controls how fast operations take place within the computer take place, sends a steady stream of digital pulses to the interval between pulses are called cycles
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Speed measurement units for various computer categories
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MHz, GHz for PCs, MIPS for workstations and mainframes, FLOPS for supercomputers CPU
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Parallelism & Pipelining
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Executing operations of more than one instruction at the same time
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Interleaving:
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The CPU alternates communication between multiple memory banks
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Bursting
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The CPU retrieves data from multiple consecutive addresses in memory
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Hyperthreading
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The CPU handles multiple simultaneous requests from the OS or software
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RAM (Random Access Memory):
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Temporarily stores program instructions and data,volatile, various types: DRAM, SDRAM, DDR-SDRAM, etc.
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ROM (Read Only Memory):
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Stores fixed start-up instructions such as the BIOS, non-volatile, some types can be re-programmed (flashing the ROM)
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CMOS
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Stores flexible start-up instructions such as time, date, and calendar, it is powered by a battery, non-volatile
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Flash
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Stores programs and data, non-volatile
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Cache
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Temporary storage for instructions and data that the processor is likely to use frequently
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Level 1 (L1) Cache
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part of the processor chip
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Level 2(L2) Cache
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may or may not be a part of the processor
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Level 3
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cache is optional
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Expansion Slots
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Sockets on the motherboard into which expansion cards can be plugged, open vs. closed architectures
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Expansion Slots
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Sockets on the motherboard into which expansion cards can be plugged, open vs. closed architectures
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Expansion Cards
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Circuit boards that provide more memory or control peripheral devices
Include graphic, sound, modem, network interface, and PC cards |
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Common Buses connect cards to motherboard
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Include ATA/IDE, PCI, PCI Express, AGP
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Ports
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Connection socket or jack on the outside of the system unit into which different types of cables can be plugged
Include serial, parallel, SCSI, USB, FireWire, dedicated, IrDA, MIDI, Bluetooth, Ethernet ports |
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Secondary Storage
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Hard disks
Smart cards Optical disks Online Storage |
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The storage hierarchy
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Bits
Characters Fields Records Files |
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Types of Databases
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Individual
Shared Distributed Public databanks Object oriented |
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The relational database model
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It relates data in different files through the use of the key field or a common data element
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Schema
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objects (entities) represented in the DB and the relationships between them
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Query techniques
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QBE, query languages such as SQL
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Mirroring
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multiple copies in different locations
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Reprocessing
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redoing the processing from a known past point
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Rollforward
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a variant of reprocessing
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Rollback
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undoing unwanted changes
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Data Mining
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the computer-assisted process of sifting through and analyzing vast amounts of data in order to extract meaning and discover new knowledge
Data sources |
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The Database Management System
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A program that controls the structure of the database and access to the data
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The advantages of DBMSs
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File sharing
Reduced data redundancy Improved data integrity Increased security Ease of data maintenance |
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Features of DBMSs
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Data dictionary
Utilities Report generator Access security |
