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Chapter 12 Information system Software that helps the user organize and analyze data Electronic spreadsheets and database management systems Software tools that allow the user to organize, manage, and analyze data in various ways Spreadsheet A software application that allows the user to organize and analyze data using a grid of labeled cells – A cell can contain data or a formula that is used to calculate a value – Data stored in a cell can be text, numbers, or “special” data such as dates – Spreadsheet cells are referenced by their row and column designation The power of spreadsheets comes from the formulas that we can create and store in cells – When a formula is stored in a cell, the result of the formula is displayed in the cell – If  we’ve  set  up  the spreadsheet correctly, we could • add or remove tutors. • add additional weeks of data. • change any of the data we have already stored and the corresponding calculations would automatically be updated. – Formulas make use of basic arithmetic operations using the standard symbols (+, -, 2, *, and /) – Spreadsheet functions – Computations provided by the spreadsheet software that can be incorporated into formulas – Range – A set of contiguous cells specified by the endpoints Circular reference A set of formulas that ultimately rely on each other Possible tasks a spreadsheet could perform: • Track sales • Analyze sport statistics • Maintain student grades • Keep a car maintenance log • Record and summarize travel expenses • Track project activities and schedules • Plan stock purchases • Spreadsheets are also useful because of their dynamic nature, which provides the powerful ability to do what-if analysis • Database • A structured set of data • Database management system (DBMS) • A combination of software and data, made up of a physical database, a database engine, and a database schema • Physical database • A collection of files that contain the data • Database engine • Software that supports access to and modification of the database contents • Database schema • A specification of the logical structure of the data stored in the database • Database query • A request to retrieve data from a database Relational DBMS A DBMS in which the data items and the relationships among them are organized into tables Tables A collection of records Records (object, entity) A collection of related fields that make up a single database entry Fields (attributes) A single value in a database record Key One or more fields of a database record that uniquely identifies it among all other records in the table We can express the schema for this part of the database as follows: Movie (MovieId:key, Title, Genre, Rating) Structured Query Language (SQL) A comprehensive relational database language for data manipulation and queries select attribute-list from table-list where condition name of field name of table value restriction select Title from Movie where Rating = 'PG' Result is a table containing all PG movies in table Movie Entity-relationship (ER) modeling A popular technique for designing relational databases ER Diagram A graphical representation of an ER model Cardinality constraint The number of relationships that may exist at one time among entities in an ER diagram Electronic commerce The process of buying and selling products and services using the Web. Chapter 16 The Web An infrastructure of information combined and the network software used to access it Web page A document that contains or references various kinds of data Links A connection between one web page and another Website A collection of related web pages Web browser A software tool that retrieves and displays eb pages Web server A computer set up to respond to requests for web pages Uniform Resource Locator (URL) A standard way of specifying the location of a Web page, containing the hostname, "/", and a file Instant messaging (IM) An application that allows people to send and receive messages in real time – Both sender and receiver must have an IM running – Most IM applications use a proprietary protocol that dictates the precise format and structure of the messages sent – Instant messages are not secure Blog or Weblog – An online journal or newsletter that is frequently updated and intended for public consumption Cookie A small text file that a web server stores on your local computer’s hard disk – A cookie contains information about your visit to the site – Cookies can be used • to determine number of unique visitors to the site • to customize the site for future visits • to implement shopping carts that can be maintained from visit to visit – Cookies are not dangerous – Hypertext Markup Language (HTML) – The language used to create or build a Web page – Markup language – A language that uses tags to annotate the information in a document Tags – The syntactic element in a markup language that indicates how information should be displayed – Tags are enclosed in angle brackets () – Words such as HEAD, TITLE, and BODY are called elements and specify the type of the tag – Tags are often used in pairs, with a start tag such as and a corresponding end tag with a / before the element name, such as The browser determines how the page should be displayed based on the tags The browser – Ignores the way we format the HTML document using carriage returns, extra spaces, and blank lines – Takes into account the width and height of the browser window – Reformats the contents to fit your browser window Attribute – Part of a tag that provides additional information about the element – attribute-name = value – – inserts the image stored in file "myPicture.gif" Java applet – A Java program designed to be embedded into an HTML document, transferred over the Web, and executed in a browser JSP Scriptlet A portion of code embedded in an HTML document designed to dynamically contribute to the content of the web page Java Server Page A web page that has a JSP scriptlet interwoven among the HTML content A JSP scriptlet is encased in special tags beginning with Imagine JSP scriptlets as having the expressive power of a full programming language JSPs are executed on the server side where the web page resides By the time it arrives at your computer, all active processing has taken place, producing a static (though dynamically created) web page JSPs are particularly good for coordinating the interaction between a web page and an underlying database Extensible Markup Language (XML) A language that allows the user to describe the content of a document – HTML describes how a document should look – XML describes a document's meaning Metalanguage A language for talking about, or defining, other languages XML is a metalanguage XML represents a standard format for organizing data without tying it to any particular type of output Extensible Stylesheet Language (or XSL) A language for defining transformations from XML documents to other output formats Chapter 2 Natural Numbers Zero and any number obtained by repeatedly adding one to it. Examples: 100, 0, 45645, 32 Negative Numbers A value less than 0, with a – sign Examples: -24, -1, -45645, -32 Integers A natural number, a negative number, zero Examples: 249, 0, - 45645, - 32 Rational Numbers An integer or the quotient of two integers Examples: -249, -1, 0, 3/7, -2/5 How many ones are there in 642? 642 is 600 + 40 + 2 in BASE 10 The base of a number determines the number of digits and the value of digit positions What if 642 has the base of 13? 642 in base 13 is equivalent to 1068 in base 10 Decimal is base 10 and has 10 digits: 0,1,2,3,4,5,6,7,8,9 Binary is base 2 and has 2 digits: 0,1 With distinct symbols for 10 and above. Base 16 has 16 digits: 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E, and F What is the decimal equivalent of the hexadecimal number DEF? What is the decimal equivalent of the octal number 642? What is the decimal equivalent of the hexadecimal number DEF? What is the decimal equivalent of the binary number 1101110? Converting Binary to Octal Converting Binary to Hexadecimal Converting Decimal to Octal What is 1988 (base 10) in base 8? Converting Decimal to Hexadecimal What is 3567 (base 10) in base 16? Chapter 3 Computers are multimedia devices,dealing with a vast array of information categories Computers store, present, and help us modify • Numbers • Text • Audio • Images and graphics • Video Data compression Reduction in the amount of space needed to store a piece of data Compression ratio The size of the compressed data divided by the size of the original data A data compression technique can be lossless, which means the data can be retrieved without any loss of the original information lossy, which means some information may be lost in the process of compaction Information can be represented in one of two ways: analogor digital Analog data A continuous representation, analogous to the actual information it represents Digital data A discrete representation, breaking the information up into separate elements Computers cannot work well with analog data, so we digitize the data Digitize Breaking data into pieces and representing those pieces separately Why do we use binary to represent digitized data? Important facts about electronic signals • An analog signal continually fluctuates in voltage up and down • A digital signal has only a high or low state, corresponding to the two binary digits • All electronic signals (both analog and digital) degrade as they move down a line • The voltage of the signal fluctuates due to environmental effects Signed-magnitude number representation The sign represents the ordering, and the digits represent the magnitude of the number ASCII stands for American Standard Code for Information Interchange ASCII originally used seven bits to represent each character, allowing for 128 unique characters Later extended ASCII evolved so that all eight bits were used The first 32 characters in the ASCII character chart do not have a simple character representation to print to the screen The Unicode Character Set Extended ASCII is not enough for international use One Unicode mapping uses 16 bits per character How many characters can this mapping represent? Unicode is a superset of ASCII The first 256 characters correspond exactly to the extended ASCII character set Assigning 16 bits to each character in a document uses too much file space We need ways to store and transmit text efficiently Text compression techniques keyword encoding run-length encoding Huffman encoding Audio Formats Audio Formats – WAV, AU, AIFF, VQF, and MP3 MP3 (MPEG-2, audio layer 3 file) is dominant – analyzes the frequency spread and discards information that can’t be heard by humans – bit stream is compressed using a form of Huffman encoding to achieve additional compression – Color – Perception of the frequencies of light that reach the retinas of our eyes – Retinas have three types of color photoreceptor cone cells that correspond to the colors of red, green, and blue color depth The amount of data that is used to represent a color HiColor A 16-bit color depth: five bits used for each number in an RGB value with the extra bit sometimes used to represent transparency TrueColor A 24-bit color depth: eight bits used for each number in an RGB value Digitizing a picture Representing it as a collection of individual dots called pixels Resolution The number of pixels used to represent a picture Raster Graphics Storage of data on a pixel-by-pixel basis Bitmap (BMP), GIF, JPEG, and PNG are raster-grahics formats Bitmap format Contains the pixel color values of the image from left to right and from top to bottom GIF format (indexed color) Each image is made up of only 256 colors JPEG format Averages color hues over short distances PNG format Like GIF but achieves greater compression with wider range of color depths Which is better for line drawings? Pictures? Vector Graphics Vector graphics A format that describes an image in terms of lines and geometric shapes A vector graphic is a series of commands that describe a line’s direction, thickness, and color. The file sizes tend to be smaller because not every pixel is described. Vector graphics can be resized mathematically and changes can be calculated dynamically as needed. Vector graphics are not good for representing real-world images Representing Video Video codec COmpressor/DECompressor Methods used to shrink the size of a movie to allow it to be played on a computer or over a network Almost all video codecs use lossy compressions to minimize the huge amounts of data associated with video Temporal compression A technique based on differences between consecutive frames: If most of an image in two frames hasn’t changed, why should we waste space to duplicate all of the similar information? Spatial compression A technique based on removing redundant information within a frame: This problem is essentially the same as that faced when compressing still images Chapter 4 Computers and Electricity Gate A device that performs a basic operation on electrical signals Circuits Gates combined to perform more complicated tasks Boolean expressions Uses Boolean algebra, a mathematical notation for expressing two-valued logic Logic diagrams A graphical representation of a circuit; each gate has its own symbol Truth tables A table showing all possible input values and the associated output values Constructing Gates Transistor A device that acts either as a wire that conducts electricity or as a resistor that blocks the flow of electricity, depending on the voltage level of an input signal A transistor has no moving parts, yet acts like a switch It is made of a semiconductor material, which is neither a particularly good conductor of electricity nor a particularly good insulator Half adder Full adder Multiplexer A circuit that uses a few input control signals to determine which of several output data lines is routed to its output Integrated circuits (IC) are classified by the number of gates contained in them Chapter 7 Problem solving The act of finding a solution to a perplexing, distressing, vexing, or unsettled question How do you solve problems? Understand the problem Devise a plan Carry out the plan Look back Ask questions! Ask questions! Never reinvent the wheel! Divide and Conquer! Algorithms Algorithm A set of unambiguous instructions for solving a problem or subproblem in a finite amount of time using a finite amount of data Abstract Step An algorithmic step containing unspecified details Concrete Step An algorithm step in which all details are specified Two methodologies used to develop computer solutions to a problem – Top-down design focuses on the tasks to be done – Object-oriented design focuses on the data involved in the solution (We will discuss this design in Ch. 9) Summary of Methodology Analyze the Problem Understand the problem!! Develop a plan of attack List the Main Tasks (becomes Main Module) Restate problem as a list of tasks (modules) Give each task a name Write the Remaining Modules Restate each abstract module as a list of tasks Give each task a name Re-sequence and Revise as Necessary Process ends when all steps (modules) are concrete Control structure An instruction that determines the order in which other instructions in a program are executed Can you name the ones we defined in the functionality of pseudocode? Arrays As data is being read into an array, a counter is updated so that we always know how many data items were stored Sorted Arrays The values stored in an array have unique keys of a type for which the relational operators are defined Sorting rearranges the elements into either ascending or descending order within the array A sorted array is one in which the elements are in order Sorting Arranging items in a collection so that there is an ordering on one (or more) of the fields in the items Sort Key The field (or fields) on which the ordering is based Sorting algorithms Algorithms that order the items in the collection based on the sort key Selection Sort A slight adjustment to this manual approach does away with the need to duplicate space – As you cross a name off the original list, a free space opens up – Instead of writing the value found on a second list, exchange it with the value currently in the position where the crossed-off item should go Bubble Sort Bubble Sort uses the same strategy: Find the next item Put it into its proper place But uses a different scheme for finding the next item Starting with the last list element, compare successive pairs of elements, swapping whenever the bottom element of the pair is smaller than the one above it Bubble sort is very slow! Insertion Sort If you have only one item in the array, it is already sorted. If you have two items, you can compare and swap them if necessary, sorting
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