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120 Cards in this Set
- Front
- Back
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Information
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• Information: Knowledge derived from study, experience or instruction; facts significance, meaning, data that can be communicated. Communication that has value because it informs. Useless unless communicated.
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• Ways to carry information
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books, numbers, live broadcasts, direct communication—“MEDIA”
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• All media can be represented digitally
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pattern of simple numbers and digits—0 and 1—binary. Binary is universal language for today’s computers—DIGITIZATION—process of converting info into digital form. (Easy to store, copy, transmit)
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• Computer confluence
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computers and digital devices, telecommunications and networking, electronic entertainment and digital media
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internet
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loose connections of networks, no one entity controls internet
o Information through internet: email, web pages, entertainment, commerce o No one validates, nobody polices this information. |
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• World Wide Web
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Web is NOT the internet; one part of the internet.
o All the information on the internet that has been made available using particular method (HTML, HTTP) o Computer is part of the internet when connected; info on my computer will become part of web during lab |
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web browsers
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• Web Browsers: programs that make it easy for anyone on internet to access information on the web (Mozilla)
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• History of the internet
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o US military project from 1960s: ARPANET—designed to survive nuclear attack. Expanded into academics and research in the 1970s; separated from MILNET in ‘80s. Originally only non-commercial uses allowed.
o ARPANET 1980: 75 sites. Now: 285,000,000 sites o 6 original top level domains: edu, gov, org, net, (make network work) mil, com, int o International domains: us, ca, uk, jp, fr, de (germany), tv (Tuvalu islands) |
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• History of the WWW
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o Invented by Tim-Berners-Lee at CERN (1989)
o Originally designed for distributing scientific results; text based browsers o First graphical browser (Mosaic) 1993-U of IL; expanded by Netscape o ‘Ban’ on commercial traffic on web lifted after Mosaic released; .com becomes largest domain o E-commerce explosion 1990s |
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• Node
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computer connected to network. 1971: 18 internet nodes 2005: 353, 284,000 internet nodes
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• Client/Server Paradigm:
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o Clients: request, receive, display information (web browsers—request, receive, display web docs)
o Servers: store info, process requests from clients, send information to clients in response to requests (web sites are servers—store web info, process browser requests) o Peers: nodes that can act as either or both o Requires common protocol and language so clients and servers can communicate o Protocol used: HTTP-Hypertext Transfer Protocol; method by which browsers and servers communicate |
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HTML
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: hypertext markup language—actual description of content and layout of page
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o Addresses used by clients to find servers are URLS
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Uniform Resource Locators:
• URL: http://www.wfu.edu/~kellba/csc101/index.htm protocol----server----directory (folder)----document/file |
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• Other protocols:
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https: ftp: file: (set of rules for having conversation)
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• HTTP
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defines how browsers and servers communicate;
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HTML
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defines content and structure of web pages
o Hypertext: text docs containing hyperlinks; cross references o Markup: text size, bold, headings v. body text, column layout, etc o Language: standardized set of instructions for a computer o Platform independent (any computer, any browser-should look the same) o Resolution independent: any screen or printer size/quality—page should look the same o Multimedia: text, images, video, sound can be combined on each page o Hyperlinked: immediate clickable links to other content; local or remote o Flexible: allows for the addition of new, unexpected technologies o Consists of plain text with markup tags (Plain text-standard text characters) Markup tags: embedded commands or codes (within plain text that describe content and structure) o Tags—non-case sensitive; many are ‘paired tags’ o Simple text enclosed in paragraph tags; automatically wraps to fit the window o Break tags help to format lines o Font face, color, style, etc. may also be specified. o Absolute font sizes: between 1 and 7; relative: use a number +n or –n… “basefont” size is 3 o Basic doc structure: <html> <head>--description of document and scripts </head> <body> </body> </html> o Titles appear in taskbar and browser’s title bar o 3 kinds of lists: ordered (automatically numbered ), unordered (bullet points), definition lists (terms and defs) o Clicking on hyperlink: automatic information request to a server. |
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• Portal
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website that acts as an entry point to the web. Can use portal as homepage
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• Internet search engines
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o Index the web; automatic and manual methods
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o Automatic indexing of the web:
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websites found by special software called ‘robot,’ web crawler or spider
Run forever looking for links; every page it finds is added to the list; relevance ranking based on content Very large and comprehensive lists; too much info, little quality control |
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o Manual indexing
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Examined by people. Organized into topics, only relevant sites listed; less comprehensive
o Most are a combination; META search engine—automated gateways into many other search engines; search all included search engines simultaneously * often redundant results, less control ** Dogpile, Sherloc |
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• Abacus
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first developed in Babylonia 5000 years ago; Decimal system: 11th century; Algebraic symbols: 16th century.
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• William Schnickard,
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Germany, Basic mechanical calculator—just addition and subtraction c. 1600
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• Blaise Pascal
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: Pascaline: addition and subtraction only
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• Gottfried Wilhelm von Leibniz
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Germany: Stepped reckoner—all four arithmetic functions
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• Charles Babbage
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England 1791-1871; first pioneer of modern digital computing machines
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• Difference engine
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special purpose machine designed to calculate and print navigational tables
o Method of differences to solve polynomials; never really worked |
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• Analytical engine:
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general purpose machine; programmable;
o based on idea of Jacquard loom; fabric pattern stored on punch cards o Had basic parts of modern computer: input/output, “Mill” (processor), store (Memory) • Analytical engine: first general-purpose digital computing device |
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• Konrad Zuse:
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1910-1995: Between 1936 and 1943 designed a number of general-purpose computing machines; electromechanical relays—not electronic
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• Howard Aiken and Grace Hopper
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o Aiken designed; Hopper programmed the Harvard Mark 1 1944; used by Navy for ballistic and gunnery table calculations; electromechanical relays
o Hopper’s group found first computer bug—caused the Mark 1 to fail (moth) o Hopper invented the Compiler |
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• John Atanasoff:
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built ABC machine 1939
o First electronic digital computing machine; vacuum tubes instead of relays—smaller and faster o Special purpose machine for solving simultaneous equations; first to use binary numbers |
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ENIAC team at UPenn
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o ENIAC: Electronic Numerical Integrator and Computer—first electronic, general-purpose digital computer.
o Manually programmed; commissioned by US Army during WWII o Completed 1946; Massive scale (30 tons), redundant design; data encoded internally in decimal o Later models: general use (ENIAC) not specific purpose; add series of #s together o Manually programmed by boards, switches, digit trays |
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• John von Neumann
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o Hungary; developed the stored program concept—no more manual programming!
o Helped Mauchly and Eckert develop the EDVAC Electronic Discrete Variable Computer o Conceived cold-war principle of Mutually Assured Destruction o Designed IAS machine—“von-Neumann Architecture Stored program: data and programs both stored in memory Data and programs internally encoded in binary 3 main parts of computer organization: CPU (Central Processing Unit) • Serial uni-processor design • Program interpretation cycle • Fetch, decode, execute Main memory data and program I/O Input/output |
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• Maurice Wilkes
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built EDSAC: Electronic Delay Storage Automatic Calculator; first stored-program general purpose electronic digital computer; first to use symbolic programming language (assembly language)
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• Alan Turing:
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Developed simple, abstract, universal machine model for determining computability; Led ULTRA project that broke the code for Germany’s Enigma machine during WWII
o Constructed Colossus—used to crack Enigma Code; 2400 vacuum tube; helped end WWII • Commercial Computers: o UNIVAC: 1951; Mauchley and Eckert: US Census Bureau; Prudential—first commercial, general-purpose computer system. Vacuum tubes, liquid mercury memory tanks o IBM System 360: 1964: Solid-state circuits (transitors and integrated circuits) o DEC PDP Series: Minicomputers; Cray 1: 1976: Supercomputers—advanced designs; number crunching |
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• Personal Computers
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first ones late 1970s, (Apple II, Commodore PET, Atari AMIGA) IBM PC 1981, MAC 1984
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• Clusters and grids:
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many inexpensive computers working together to solve large problems: Cluster—all one location—Grid—spread over many locations but working together.
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• Moore’s Law:
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Predicted in 1971 that number of transitors on a chip (and its speed) would double every year. Actually—doubles every 2 years; price/performance doubles every 1.5 years
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• To process info
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input info, process info (perform operation), output results
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• Computer
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machine that processes info; not necessarily only digital information
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• Analog information:
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what we experience in the real world: sights, sounds, textures, smells, continuous and infinitely variable (Temperature outside over the course of one day)
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• Analog computer:
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mechanical thermostat: input (measured temp)—program: if temp is greater than setpoint, AC on—Output—action of turning AC on or off
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• Digital information:
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discrete; distinct, precise—measuring temperature with a digital thermometer
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• Analog v Digital info:
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Advantages of digital: greater precision, efficient storage and transfer, unlimited absolute replication, easily manipulated; not many analog computers today
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• Bits and Bytes:
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o Single bit: 1 or 0; (binary digit); smallest atom of data; yes/no, on/off
o One bit can only represent 2 things; 2 bits can represent 4 things; 00, 01, 10, 11 o Eight bits can represent 256 things; 8 consecutive bits is called a byte o 1KB: 1000 bytes (2^10); 1MB: 1000 KB (1 million bytes); 1GB 1000 MB; billion bytes; TB: 1000 GB-1 trillion bytes; 1PB (petrabite)—1000 TB, quadrillion bytes o Byte---KB---MB----GB----TB----PB |
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• Digital information:
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digital computers process digital information
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• To digitize text letters
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convert to binary representation ASCII: American Standard Code for Information Exchange
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• Digitizing analog information:
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text and numbers are discrete; analog info is continuous; non-discrete
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• Sampling
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discrete samples chosen to represent continuous data; choose discrete pixels (picture elements)
• Tradeoff between image quality and file size |
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• Quantizing
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each sample assigned particular number
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• Parts of a computer:
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o Central processor
o Main memory o Secondary storage devices o Input/output devices o Main parts of computer are on the motherboard o Motherboard: Expansion slot, CPU, Memory modules (RAM), expansion cards |
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Von Neumann Architecture
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• All modern computers follow logical model of computing
o CPU, Main memory (active data, programs), I/O subsystem (i/o devices—peripherals; secondary storage: mass storage) |
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• Main memory:
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o fast access, binary storage, active data and program instructions; main memory divided into words; standard, fixed size; 4 bytes per word
o Each word has unique address in memory o Main memory—generally RAM (Random Access Memory)—Readable, writable, general use, volatile—disappears when powered off. o RAM is main memory, not hard disk. Disk storage is secondary storage. More RAM-more $; doesn’t make computer faster; lets you do more stuff. |
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• Program Interpretation Cycle:
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o COY executes programs one instruction at a time
o Fetch (a word from main memory), decode (instructions in that word), Execute (those instructions) repeat o Each CPU has list of simple operations—instruction set |
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• Machine Language:
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o Each CPU has its own specific machine language
o Limited capabilities; limited instruction sets o Data movement operations: move data from main memory to CPU, move data from one memory location to another, move data to or from secondary storage, input and output o Arithmetic and logical operations: arithmetic on simple integers, comparisons o Program Control operations: start program, end program, skip to a different instruction, test data to decide what to do next |
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• Secondary storage—
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main memory contains data and instructions that are in active use; auxiliary storage for data and programs. Permanent, greater capacity possible; infinite expansion; much cheaper per MB than RAM, much slower than RAM.
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• Main memory:
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Volatile, limited capacity, more expensive, high speed access
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• Secondary storage devices based on
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capacity, speed, cost, permanence
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• Types of Secondary Storage:
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o Random access: data words addressed individually; access time is constant USB flash drives, memory cards
o Direct access: DASD: independently addressed in regions; most common form of secondary storage used in PCS: floppy discs, hard discs, CD, DVD o Sequential access storage devices: SASD: data items organized in linear sequence; access time highly variable; items near beginning of sequence accessed quickly-at the end, may take a long time MAGNETIC TAPE o Memory/storage hierarchy: see sheet |
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• Magnetic tape:
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o Audio cassettes, VHS—many formats and sizes—used for archival purposes. UNIVAC, IBM system 360—tape drives provided online storage when hard disks were too expensive
o Archival data storage: not appropriate for online storage, cheap, compact, need to change tapes frequently; tape libraries—trillions of bytes of data o Bits can be represented by magnetization of tiny metallic particles on surface of a strip of tape. Aligned particles pointing one way represent 0; other way represent 1 o Composed of large number of microscopic magnetic particles; different sections of tape can be magnetized oppositely; sections of tape have one of 2 sides, can represent binary information . |
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• Direct Access Storage Devices
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magnetic hard discs and floppy disks; all arranged in TRACKS and SECTORS
• Each sector contains many words of data • Seek time: read/write head advances to proper track • Latency time: wait for proper sector to rotate under read/write head • Read/write time: read/write head scans sector for read or write • Data transfer rate: average rate of sending or retrieving data from the disk |
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• CD-ROM: Compact Disk—Read only Memory
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o Factory-produced for published info
o Binary data stored as depressions (PITS) on a metallic surface (LAND) Pits=1, Land =0 o Laser beam reads data by reflecting off pit and land areas |
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• CD-R
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o CD-Recordable; burned by desktop devices, readable by CDROM readers
o Disks individually written; burned o High intensity laser burns darkened dye spots on grooved tracks. 1=spot; 0=no spot o Laser reads data by reflecting off dye spots |
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• CD-RW
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o Disks individually written; laser aligns microscopic crystals in grooved tracks; aligned crystals look dark; unaligned look bright dark =1, bright =0
o Online storage; erasable |
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• Input/Output:
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• Generally called peripherals—around the outside of computer’s main computational activities
• Input: Devices for converting info into a form understandable by computers Keyboard, mice, scanner, digital camera • QWERTY: layout designed to slow down old mechanical typewriters; Dvorak keyboard • Output: CRT (Cathode Ray Tube), LCD (Liquid Crystal Display)—Video Displays; printers, speakers • CRT Displays: o Glass screen coated with phosphorus—glows when excited; beams of electrons (cathode rays) focused on screen—one for each red, green, blue—brightness varied by strength of beam o Re-scans many times a second: refresh rate • LCD Displays: o What you have on your laptop; flat-screen tvs o Behind glass are thin layers of dyed liquid crystals—red, green, blue o Electrical charge applied across thin layers causing the crystals to align such that they are either visible or invisible • Plasma displays: larger displays, small bubbles with special gasses, gasses glow when electric charge is applied; different gasses give different colors • Printers: o Character based: print individual letters; characters-bad for graphics o Page-based: laser/inkjet printers o Print each dot (pixel); versatile |
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• Hardware
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physical devices and equipment
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• Software
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commands and instructions that tell the hardware what to do
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program
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• Set of instructions to perform particular task
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• Creating a program
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coding, programming
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• Application
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program that performs some useful job
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• Program
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list of instructions that direct computer’s processes; developed and written using symbolic programming languages (high-level; easier to create and comprehend)
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• Low level programming:
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CPU good at executing simple binary instructions—can’t solve complex problems
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• Machine language:
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binary code
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• High-level
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complex function• Programs written in high-level languages must be translated into machine language:s
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• Compilation
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o entire program translated by compiler into machine language to form a binary executable file .exe
o Efficient- happens ONCE where software is produced; better for complex programs BOTH act on software, not on data Compilation: when and where software is made; Interpretation: on the computer running program when it’s run |
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• Interpretation
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o Happens every time you run a program
o Program is translated at run-time; one line at a time, on computer that is running the program; not as efficient as compilation; portable, not machine specific, good for web-based applications. BOTH act on software, not on data |
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• Software development cycle:
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• Analyze and understand task
• Devise a plan o Expressed by algorithm—consider what info is needed to perform the task, precise sequencing of events necessary to complete task, how to react to unexpected situations o Plan for solving problem • Create a program that implements the plan o Programming: translating of algorithms into specific high-level language o Coding less than 10% of work done on project • Test and correct the program |
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• Software releases
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• Alpha: initial pass, for internal use only
• Beta: first external release, only to select group of users • Version 1.0: first commercial version (Additional minor versions: 1.1, 1.2, 1.3, etc.) Additional major versions: 2.0, 3.0 |
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division of labor
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• System analysts: responsible for planning, designing, overseeing software projects
• Software engineers (programmers) work in groups to implement parts of the overall design • Quality assurance groups: conduct independent testing |
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• Client-side scripts
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: best for simple tasks. Server-side scripts: handle much larger tasks
• Client-side: dynamic, interactive: page changes based on user input; page is generated by a script—portable |
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• Server side scripts
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run on remote server (amazon.com—want the server, not the client to do the work finding books—banking, airline reservation, MP3s—less efficient for simple tasks)
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o Sequential search:
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server checks each book in the catalog to see if it’s the desired book; best/worse case scenarios
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o Binary search:
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divide and conquer approach; pseudo-code: start with ordered/alphabetized list; look at middle item in list; continue search on half of list that contains the item: search on 1,000,000 items takes only 20 comparisons
o For binary search to work, data must already be in order; sorting is a harder job than searching |
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• Development of Unix:
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o Generic term for common operating system for small-to-midzsize multi-user computers
o Initially developed by Bell Labs in NJ o Designed to be simple and elegant; written in high-level language o Modular design—central functions in a kernel o Included networking in the basic design |
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• Linux
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o New OS; full-featured, professional, free OS
o Open-source—source code is available to anyone; can be adapted to individual circumstances o Licensed using GPL: general public license o Not built by a single company—commercial support originally hard to find—installation and customization o Widely used on large web servers and large computational clusters o Becoming more widely used as a desktop operating system o Most mainframe computes have used proprietary OS—specific to manufacturer’s products |
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• Intellectual property:
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something intangible; creative expression of ideas
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• Trademarks
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protect words, names, symbols, colors and smells
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• Patents
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protect inventions, devices and processes, not ideas
o Awarded for inventions that ‘promote the progress of science and useful arts’ o 17 years validity period o Software generally protected through copyright rather than patent |
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• Copyrights
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to protect creative expression of thoughts and ideas
• Copyright owner: o Reproduce work, prepare derivative works, distribute copies, perform or display work publicly o Works must be: original, creative, fixed in tangible medium—exists immediately upon creation of work—registration not required • Copyright law: covers literary works, live and recored music, drama, dance, architecture, computer software • Principle of fair use: personal, education, science, journalism • Fair use: purpose and character, nature of original work, amount copied, effect of its use on its potential market |
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• Sound
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analog phenomenon: rapid vibrations (pressure fluctuations)—transmitted through the air or other medium
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• Size
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amplitude; speed-frequency
• Larger amplitude vibrations: louder sound • Higher frequency vibrations: higher pitch • Frequency: Hz |
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• Middle C:
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262 Hz
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• Human hearing in range
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of 20 Hz to 20,000 Hz
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• ‘Pure sound’
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is vibration with single frequency—natural sounds are complex vibrations
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• Digitizing sound:
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sampling, quantizing
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• Sampling rate:
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number of discrete samples per second
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• Resolution
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accuracy of quantized amplitude due to number of levels of quantization—bit depth
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• Dynamic range:
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range of quantized amplitude values
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• Niquist’s Theorem
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sample rate must be at least twice desired frequency
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• Resolution
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number of bits used to store amplitude data: bit depth
• Using more bits gives us more amplitude levels; higher bit depth allows for higher resolution of the sound |
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• Dynamic range:
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difference between softest and loudest sounds that can be stored –clipping occurs when info is lost
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circuits
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oscillators
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• MIDI
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standard interface between electronic musical instruments, synthesizers and keyboards-Musical instrument digital interface
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• Speech synthesis
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easier of the problems—input is text characters; obv. Approach: recorded dictionary of all words
o Better approach: phonemes: English uses only about 50 phonemes for all possible words—still need to look at context |
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• Speech recognition:
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: much harder problem than speech synthesis: input-natural speech-highly variable and ambiguous; different speakers, different inflections, etc.
o Limited vocabulary: recognize speech from many different speakers and environments o Useful in controlled situations o Speaker dependent o Dictation systems; commonly trained to individual’s voice |
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• Aspect ratio:
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ratio of horizontal to vertical
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• Three color models:
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o RGB Red green blue—additive primary colors
o CMYK: cyan magenta, yellow, black—subtractive primary colors—pigments, printing—white means no ink, dark means a lot of ink o HSB: Hue Saturation Brightness –how artists perceive color o Indexed color: way to avoid storing unnecessary info in image file—set of chosen colors is called a palette. |
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Picture resolution
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number of pixels
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• Lossless compression:
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after compression and decompression, original image is reproduced exactly
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• Database management system
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software that runs database
• Contain large sets of data in multiple files with interconnections |
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• Originally in flat files
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stored in tables, tables contain rows of data called records; records consist of individual data elements called fields …data unnecessarily duplicated, sorting is hard, poor data control
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• Network database model
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separate tables used to avoid data redundancy—connected through physical disk address links
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• Database
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computerized data storage—data storage devices and standardized methods for adding, retrieving, changing data
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• Codec
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compressor/decompressor
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• GIF
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graphic interchange format: indexed color, lossless—graphics
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• Jpeg file
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lossy joint photographic experts group ideal for photographs
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• Lossy:
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exact reproduction not guaranteed
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• Relational database model:
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does not depend on physical arrangement of data storage elements; logical relationships of the data—connected through logical links—primary key for each table is indexed; data not redundant, well controlled, less efficient than network model—not high-speed.
• Tradeoff between efficiency and flexibility |
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• Network
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ATMs, banking, airline ticketing (transaction based systems that don’t need to be flexible)
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• Relational
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on-demand flexibility: sales, market data, sports stats
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• Errors in ASCII data
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7 binary bits used to represent each text character; extra parity bet used to detect transmission errors
• Odd parity error detection: transmitter sets parity bit so that the total number of 1 bits in the byte is an odd number • Even parity bit: set to make total number of 1 bits an even number • Receiver checks parity—if total of 1 bits is not correct, indicates an error |
