1. Console and GUI Programs
Two Models for Programming
This is used for C++, Java and VB.
Check which one is most current.
Copyright © Curt Hill

2. Paradigms Pronounced Pair-a-dime Definition: A model or example
A way of approaching a situation that affects every action that is taken
Copyright © Curt Hill

3. Operating Systems A set of programs that runs the computer
Performs a number of important functions:
Interprets user commands
Establishes a file system
Handles errors
Among other things
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4. User commands Early operating systems used console input
These include DOS, UNIX, VMS
Later operating systems adopted a GUI
Graphical User Interface
Pronounced “Gooey”
These include Mac OS, Windows, Xwindows
The two use different computing models
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5. Simple Example
The Console and GUI program will be demonstrated using a program to compute greatest common factor
Each program will receive two numbers from the user
Compute GCF using Euclid’s method
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6. Euclid’s Method for GCF
Make the larger num1 and smaller num2
Divide num1 by num2 and keep remainder
Set num1 to num2
Set num2 to remainder
Repeat the division until num2 < 2
Copyright © Curt Hill

7. The Console Version
This program computes the Greatest Common Factor using Euclid's method
Enter the first number
323
Enter the second number
437
GCF is 19
Do you want to do another? n
Copyright © Curt Hill

8. The GUI Version
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9. The Console Screen Usually a list of messages and inputs
When a program writes a message
Appears on the bottom of the list
All previous messages scroll up
When input is needed the user types it at bottom
No need for a pointing device, like a mouse
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10. The Console Paradigm
The model for computing is that the program is in control
It starts executing at some designated point
Continues from there
If it needs input, it initiates the input
Prompts user and then reads
The order of input is determined by program
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11. Form of Console ProgramOS
Pgm
Subr
Subr
Subr
Subr
Subr
Subr
Service
Service
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12. Form Again
In a console program the Operating System starts the main program
This program may in turn call subroutines
Methods, functions, procedures
These may call others
Some will call OS services
Such as input and output
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13. Other Console Comments
Interrupts are used by OS but not a factor in programs
Interrupt:
A response to an event whose timing is unpredictable
When interrupt processing is done, whatever was running is resumed
Copyright © Curt Hill

14. The GUI Screen Usually a series of Windows
Each window has certain characteristics and controls
A control is an item within the window
Buttons
Edit boxes
List boxes
Copyright © Curt Hill

15. GUI History Developed at Xerox Palo Alto Research Center
Alan Kay and others
They were not going to market it
Jobs of Apple saw it and used for Mac
Gates developed Windows because of success of Mac
Xwindows was developed for UNIX independently
Copyright © Curt Hill

16. WIMP The classic GUI is also known as WIMP Windows Icons Menus
Pointer (mouse or trackball)
Copyright © Curt Hill

17. The GUI Paradigm
The model for computing is that the operating system and user is in control
The program starts
It displays its windows through the operating system
Then waits for the user to do something
Most of the execution is in response to some user action, communicated by the OS
Copyright © Curt Hill

18. A Sample Window
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19. Form of GUI Program OS Pgm Subr Subr Subr Subr Subr Service Service
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20. Form Again
In a GUI program the Operating System starts the main program
Main program describes how windows are to be drawn
It then returns to OS
It also registers event handlers
These are subroutines
The events are things like a button click
The subroutines may call other subroutines as well OS services
Event handlers are called by OS not program
Copyright © Curt Hill

21. Objects
In many programming environments the controls are objects in the technical sense
An object is some data and code that acts on it
These objects often conform to the PME model
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22. The PME Model Properties Methods Events
Data that is part of the object and affects how it is used
Methods
Code that manipulates the object
Events
What to do if some user action occurs
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23. Properties Data that affects how the control looks or acts Examples:
The caption of a button or text of an edit box
The alignment of the text
The position: Left, top, width, height
Some of these are modified at design time and others at run time
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24. Methods Actions that can be performed at run-time on the control
Usually involves a substantial amount of programming by someone else
Clearing an edit box can be done by assigning an empty string to its text property or executing its Clear method
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25. Events When a button is clicked some action needs to be taken
An event is an action that occurs at unpredictable times, so some code handles it
Examples:
Mousing over a control
Left click, right click or double click of a control
Receiving or losing focus
Typing in a control
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26. Languages C++, SmallTalk, Java are full object oriented languages
Full support for objects, PME, inheritance, polymorphism
There are one or more full GUI development environments
Visual BASIC is half of an object oriented language
Has objects, most of PME
No inheritance, no polymorphism
Has a full GUI development environment
Copyright © Curt Hill