Programs/Algorithms

 Computer Architecture  What is a computer program?  Flow chart  Data states  Data  Variables  History – Why VB?  Procedural programming  Object oriented programming  Visual programming  Example: Hello world

 Drawn in figure 1-1  Main components:  CPU  Main memory  Secondary storage  Input devices  Keyboard  Mouse  Scanner  Camera (still/video/webcam)

 Main components (contd):  Output devices  Monitor  Printer  Software  Operating System  Application Programs

 Set of tasks/instructions  Related?  How?  Set of data (states)  Can be in main memory (temporary)  Can be persistent  Long-term  Often stored in a database or data file

 Help visualize the flow of the program. Shows mainly the instructions and decisions  Is a blueprint for the logic in how to write the program  Historically, different symbols used for different types of logic  Variable assignment  Decisions

 Symbols:  Start/End of program: Ovals  Flow of control: Arrows  Actions: Rectangle  Input/Output: Parallelogram  Conditional: Diamond

 Variables are ESSENTIAL in programming  Variables hold things  Data  State  Variables typically have names that are meaningful  Descriptive is better  Older languages only allowed one letter  i, j, etc…  Now they can be as long as needed

 Sometimes use underscore (_)  sum_total  number_of_tries  “CamelCasing”  Start each word with a capital letter  No underscores  Ex:  SumTotal  NumberOfTries

 Hello World  No data  No states  Just a control flow  Gross pay calculator  Data: Hours worked, hourly pay rate  Ask them to exit  Or exit button (control)

 Create flowchart on board  Demo of example programs

 Procedural programming  Original style  Set of steps (including Input/Output)  Goes from “Start” to “End”  Can be shown in a flow chart easily  More difficult to reuse code

 Object-Oriented programming  Current style  Create “objects” that mimic real-world things  Ex: Automobile  Objects have properties (data)  Objects have methods (actions)  Car example. What are properties, methods  Properties: Color, Location, Speed, Direction  Actions: Honk horn, Speed up, slow down, turn to right

 Graphical User Interface (GUI)  Many, many objects have been created for visual objects  Makes it easier to program  Looks great  Don’t have to “reinvent the wheel”  Graphical environment to write programs  Graphical environment to debug programs

 GUI programming is event-driven  Screen “sits there” in a loop, waiting for user action  You write “event handlers” that handle each action that might be taken  Button clicks  Typing text  Check a checkbox  Only have to write a little bit of code at a time  Much, much easier to debug!

 Demonstrate graphical version of the two example programs