Chapter 1 - An Introduction to Computers and Problem Solving
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1 Chapter 1 - An Introduction to Computers and Problem Solving 1.2 Windows, Folders, and Files1.3 Program Development Cycle1.4 Programming Tools
2 1.1 An Introduction to Computers Create and manage a list of friends' addresses and phone numbersCalculate loan payments and amortizationComputations to support other course work
3 Communicating with the Computer Machine language – low level, hard for humans to understandVisual Basic – high level, understood by humans, consists of instructions such as Click, If, and Do
4 CompilerA compiler translates a high-level language into machine language.The Visual Basic compiler points out certain types of errors during the translation process.
5 Programming and Complicated Tasks Tasks are broken down into instructions that can be expressed by a programming languageA program is a sequence of instructionsPrograms can be only a few instructions or millions of lines of instructions
6 All Programs Have in Common: Take data and manipulate it to produce a resultInput – Process – OutputInput – from files, the keyboard, or other input deviceOutput – usually to the monitor, a printer, or a file
7 Hardware and SoftwareHardware – the physical components of the computerCentral processing unitDisk driveMonitorSoftware – The instructions that tell the computer what to do
8 Programmer and UserProgrammer – the person who solves the problem and writes the instructions for the computerUser – any person who uses the program written by the programmerIn this class, you are BOTH Programmer and User….NOT TYPICAL
9 Problem Solving Developing the solution to a problem Algorithm – a step by step series of instructions to solve a problemProblems are solved by carefully reading them to determine what data aregiven and what outputs are requested. Then a step-by-step procedure is devised toprocess the given data and produce the requested output. This procedure is called analgorithm. Finally, a computer program is written to carry out the algorithm.Algorithms are discussed in Section 2.2.
10 Visual Basic 2010BASIC originally developed at Dartmouth in the early 1960sVisual Basic created by Microsoft in 1991Visual Basic 2010 is similar to original Visual Basic, but more powerfulReleased Last Summer (2010)
12 1.2 Windows, Folders, and Files Windows and Its Little WindowsMouse ActionsFiles and Folders
13 Windows and Its Little Windows Difference between Windows and windows.Title bar indicates if window is active.
14 Mouse Actions: Hover Drag and drop Click Right-click Double-Click Pointing means moving your mouse across your desk until the mouse pointer is overthe desired object on the screen.Hovering means to linger the mouse at a particular place and wait for a message ormenu to appear.Clicking (sometimes people say single-clicking) means pressing and releasing theleft mouse button once. Whenever a sentence begins “Click on ,” you need to1. move the mouse pointer until it is at the object you are supposed to click on and2. press and release the left mouse button.An example of a sentence using this jargon might be “Click on the button marked Yes.”You also will see sentences that begin “Click inside the ” This means to move themouse pointer until it is inside the boundaries of the object, and then click.Double-clicking means clicking the left mouse button twice in quick succession(that is, pressing it, releasing it, pressing it, and releasing it again quickly so thatWindows doesn’t think you single-clicked twice). Whenever a sentence begins“Double-click on ”, you need to1. move the mouse pointer until it is at the object you are supposed to double-clickon and2. press and release the left mouse button twice in quick succession.For example, you might be instructed to “Double-click on the little box at the far leftside of your screen.”Note: An important Windows convention is that clicking selects an object so youcan give Windows or the document further directions about it, but double-clicking tellsWindows to perform a default operation. For example, double-clicking on a folder willopen that folder.Dragging usually moves a Windows object. If you see a sentence that begins “Dragthe ”, you need to
15 Files and FoldersFile: holds programs or data. Its name usually consists of letters, digits, and spaces.Folder: contains files and other folders (called subfolders).Think of a disk as a large folder that contains several smaller folders each with its own name.The naming of folders follow th same rule as naming filesEach folder is identified by listing its name preceded by a backslashA filespec typically includes the drive, path and the filename.File is identified by a smalldirectory or folder is identified by a folder iconexecutable file: is identified by a rectangle with a thin bar across topGo over: How to create a folderto rename a folderto delete a folder or fileto Copy a folder or fileTo move a folder or file
16 Key Terms in using Folders and Files Term ExampleDisk Hard disk, flash drive, DVDFile name PayrollExtension txtFilename Payroll.txtPath TextFiles\Payroll.txtFilespec C:\TextFiles\Payroll.txtThink of a disk as a large folder that contains several smaller folders each with its own name.The naming of folders follow th same rule as naming filesEach folder is identified by listing its name preceded by a backslashA filespec typically includes the drive, path and the filename.File is identified by a smalldirectory or folder is identified by a folder iconexecutable file: is identified by a rectangle with a thin bar across topGo over: How to create a folderto rename a folderto delete a folder or fileto Copy a folder or fileTo move a folder or file
17 Windows Explorer Used to view, organize, and manage folders and files. Manage: copy, move, delete
18 Invoking Windows Explorer Right-click on Windows Start buttonClick on Explore (or Open Windows Explorer) in context menu
19 Display File Extensions (Vista & Windows 7) Click on Windows Start button.Type Folder Options into Search box.Press Enter key.Click on View tab in dialog box.Uncheck ″Hide extensions for known file types″.Click on OK.
20 Display File Extensions (Vista & Windows 7 cont.)
21 Display File Extensions (XP) Alt/Tools/Folder OptionsClick the View tab.Uncheck "Hide extensions for known file types“.Click on OK.
22 1.3 Program Development Cycle Performing a Task on the ComputerProgram Planning
23 Terminology A computer program may also be called: Project Application Solution
24 Program Development Cycle Software refers to a collection of instructions for the computerThe computer only knows how to do what the programmer tells it to doTherefore, the programmer has to know how to solve problems
25 Performing a Task on the Computer Determine OutputIdentify InputDetermine Process necessary to turn given Input into desired Output
26 Problem-Solving: Approach Like Algebra Problem How fast is a car traveling if it goes 50 miles in 2 hours?Output: a number giving the speed in miles per hourInput: the distance and time the car has traveledProcess: speed = distance / time
27 Pictorial representation of the Problem Solving Process
28 Program Planning A recipe is a good example of a plan Ingredients and amounts are determined by what you want to bakeIngredients are inputThe way you combine them is the processingWhat is baked is the output
29 Program Planning (continued) Always have a plan before trying to write a programThe more complicated the problem, the more complex the plan must bePlanning and testing before coding saves time
30 Program Development Cycle Analyze: Define the problem.Design: Plan the solution to the problem.Choose the interface: Select the objects (text boxes, buttons, etc.).
31 Program Development Cycle (continued) Code: Translate the algorithm into a programming language.Test and debug: Locate and remove any errors in the program.Complete the documentation: Organize all the materials that describe the program.
32 1.4 Programming Tools Flowcharts Pseudocode Hierarchy Chart Direction of Numbered NYC Streets AlgorithmClass Average Algorithm
33 Programming ToolsThree tools are used to convert algorithms into computer programs:Flowchart - Graphically depicts the logical steps to carry out a task and shows how the steps relate to each other.Pseudocode - Uses English-like phrases with some Visual Basic terms to outline the program.Hierarchy chart - Shows how the different parts of a program relate to each other.
34 AlgorithmA step-by-step series of instructions for solving a problem (a recipe is an example of an algorithm).
35 Problem Solving Example How many stamps should you use when mailing a letter?One rule of thumb is to use one stamp for every five sheets of paper or fraction thereof.
36 AlgorithmRequest the number of sheets of paper; call it Sheets. (input)Divide Sheets by 5. (processing)Round the quotient up to the next highest whole number; call it Stamps. (processing)Reply with the number Stamps. (output)
37 FlowchartGraphically depicst the logical steps to carry out a task and show how the steps relate to each other.
41 PseudocodeUses English-like phrases with some Visual Basic terms to outline the task.
42 Pseudocode Example Determine the proper number of stamps for a letter Read Sheets (input)Set the number of stamps to Sheets / 5 (processing)Round the number of stamps up to the next whole number (processing)Display the number of stamps (output)
43 Hierarchy ChartShows how the different parts of a program relate to each otherHierarchy charts are also calledstructure chartsHIPO (Hierarchy plus Input-Process-Output) chartstop-down chartsVTOC (Visual Table of Contents) chartsAll are similar to a company’s organization chart.
45 Divide-and-Conquer Method Used in problem solving – take a large problem and break it into smaller problemsSolve the small problems first
46 Statement StructuresSequence – execute instructions from one line to the next without skipping over any linesDecision - if the answer to a question is “Yes” then one group of instructions is executed. If the answer is “No,” then another is executedLooping – a series of instructions are executed repeatedly
50 Direction of Numbered NYC Streets Algorithm Problem: Given a street number of a one-way street in New York City, decide the direction of the street, either eastbound or westboundDiscussion: in New York City even numbered streets are Eastbound, odd numbered streets are Westbound
54 Class Average Algorithm Problem: Calculate and report the average grade for a classDiscussion: The average grade equals the sum of all grades divided by the number of studentsInput: Student gradesProcessing: Find sum of the grades; count number of students; calculate averageOutput: Average gradeWe need a loop to read and then add (accumulate) the grades for each student in the class. Inside the loop, we also need to total (count) the number of students in the class. See Figures 2.8 to 2.10.grade = sum of grades / number of students.
56 Pseudocode Program: Determine average grade of a class Initialize Counter and Sum to 0Do While there are more dataGet the next GradeAdd the Grade to the SumIncrement the CounterLoopCompute Average = Sum / CounterDisplay Average
58 CommentsWhen tracing a flowchart, begin at the start symbol and follow the flow lines to the end symbol.Testing an algorithm at the flowchart stage is known as desk checking.Flowcharts, pseudocode, and hierarchy charts are program planning tools that are in dependent of the language being used.
59 Tips and Tricks of Flowcharts Flowcharts are time-consuming to write and difficult to updateFor this reason, professional programmers are more likely to favor pseudocode and hierarchy chartsBecause flowcharts so clearly illustrate the logical flow of programs, they are a valuable tool in the education of programmers