A class diagram is a pictorial representation of the detailed system design. Design experts who understand the rules of modeling and designing systems design the system's class diagrams. A thing to remember is that a class diagram is a static view of a system. The structure of a system is represented using class diagrams. Class diagrams are referenced time and again by the developers while implementing the system.
A class diagram is composed primarily of the following elements that represent the system's business entities:
Class: A class represents an entity of a given system that provides an encapsulated implementation of certain functionality of a given entity. These are exposed by the class to other classes as methods. Apart from business functionality, a class also has properties that reflect unique features of a class. The properties of a class are called attributes. Simply put, individual members of a family of our family tree example are analogous to classes in a class diagram.
As an example, let us take a class named Student. A Student class represents student entities in a system. The Student class encapsulates student information such as student id #, student name, and so forth. Student id, student name, and so on are the attributes of the Student class. The Student class also exposes functionality to other classes by using methods such as getStudentName(), getStudentId(), and the like. Let us take a look at how a class is represented in a class diagram.
Monday, March 30, 2009
vb.net open dialog box
The Open File Dialogue Box
In most programmes, if you click the File menu, and select the Open item, a dialogue box is displayed. From the dialogue box, you can click on a file to select it, then click the Open button. The file you clicked on is then opened up. We'll see how to do that from our menu. (Except, the file won't open yet - only the dialogue box will display, and then name of the chosen file. You'll learn how to open files in a later section.)
First, place two textboxes on your form. In the properties box, locate the MultiLine property. It is set to False by default (which is why you can't change the height of textboxes). Change this value to True.
Type some default text for the Text Property of textbox1. Change the Font size to 14 points.
We'll work with these textboxes when we do the Edit menu. So let's leave them for now.
When we click on File > Open from our menu, we want the Open dialogue box to appear. This is fairly straightforward in VB.NET. In fact there is even a control for it!
Open up your toolbox, and locate the control called "OpenFileDialog". You might have to scroll down to see it.
In most programmes, if you click the File menu, and select the Open item, a dialogue box is displayed. From the dialogue box, you can click on a file to select it, then click the Open button. The file you clicked on is then opened up. We'll see how to do that from our menu. (Except, the file won't open yet - only the dialogue box will display, and then name of the chosen file. You'll learn how to open files in a later section.)
First, place two textboxes on your form. In the properties box, locate the MultiLine property. It is set to False by default (which is why you can't change the height of textboxes). Change this value to True.
Type some default text for the Text Property of textbox1. Change the Font size to 14 points.
We'll work with these textboxes when we do the Edit menu. So let's leave them for now.
When we click on File > Open from our menu, we want the Open dialogue box to appear. This is fairly straightforward in VB.NET. In fact there is even a control for it!
Open up your toolbox, and locate the control called "OpenFileDialog". You might have to scroll down to see it.
Monday, March 23, 2009
Unicode
Unicode is a computing industry standard allowing computers to consistently represent and manipulate text expressed in most of the world's writing systems. Developed in tandem with the Universal Character Set standard and published in book form as The Unicode Standard, Unicode consists of a repertoire of more than 100,000 characters, a set of code charts for visual reference, an encoding methodology and set of standard character encodings, an enumeration of character properties such as upper and lower case, a set of reference data computer files, and a number of related items, such as character properties, rules for normalization, decomposition, collation, rendering and bidirectional display order (for the correct display of text containing both right-to-left scripts, such as Arabic or Hebrew, and left-to-right scripts).[1]
ASC11
ASCII stands for American Standard Code for Information Interchange. Computers can only understand numbers, so an ASCII code is the numerical representation of a character such as 'a' or '@' or an action of some sort. ASCII was developed a long time ago and now the non-printing characters are rarely used for their original purpose. Below is the ASCII character table and this includes descriptions of the first 32 non-printing characters. ASCII was actually designed for use with teletypes and so the descriptions are somewhat obscure. If someone says they want your CV however in ASCII format, all this means is they want 'plain' text with no formatting such as tabs, bold or underscoring - the raw format that any computer can understand. This is usually so they can easily import the file into their own applications without issues. Notepad.exe creates ASCII text, or in MS Word you can save a file as 'text only'.
American Standard Code for Information Interchange (ASCII), pronounced /ˈæski/[1] is a coding standard that can be used for interchanging information, if the information is expressed mainly by the written form of English words. It is implemented as a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that work with text. Most modern character-encoding schemes—which support many more characters than did the original—have a historical basis in ASCII.
Historically, ASCII developed from telegraphic codes. Its first commercial use was as a seven-bit teleprinter code promoted by Bell data services. Work on ASCII formally began October 6, 1960, with the first meeting of the American Standards Association's (ASA) X3.2 subcommittee. The first edition of the standard was published in 1963,[2][3] a major revision in 1967,[4] and the most recent update in 1986.[5] Compared to earlier telegraph codes, the proposed Bell code and ASCII were both ordered for more convenient sorting (i.e., alphabetization) of lists, and added features for devices other than teleprinters.
ASCII includes definitions for 128 characters: 33 are non-printing, mostly obsolete control characters that affect how text is processed;[6] 94 are printable characters, and the space is considered an invisible graphic.[7] The ASCII character encoding scheme is the most commonly used character set
American Standard Code for Information Interchange (ASCII), pronounced /ˈæski/[1] is a coding standard that can be used for interchanging information, if the information is expressed mainly by the written form of English words. It is implemented as a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that work with text. Most modern character-encoding schemes—which support many more characters than did the original—have a historical basis in ASCII.
Historically, ASCII developed from telegraphic codes. Its first commercial use was as a seven-bit teleprinter code promoted by Bell data services. Work on ASCII formally began October 6, 1960, with the first meeting of the American Standards Association's (ASA) X3.2 subcommittee. The first edition of the standard was published in 1963,[2][3] a major revision in 1967,[4] and the most recent update in 1986.[5] Compared to earlier telegraph codes, the proposed Bell code and ASCII were both ordered for more convenient sorting (i.e., alphabetization) of lists, and added features for devices other than teleprinters.
ASCII includes definitions for 128 characters: 33 are non-printing, mostly obsolete control characters that affect how text is processed;[6] 94 are printable characters, and the space is considered an invisible graphic.[7] The ASCII character encoding scheme is the most commonly used character set
A problem with my posts
I have done a few other posts on here, and they are not showing up, there was a few problems in the begginging and so other blogs i have wriiten havent loaded on to my blog, i will how ever find out what i had to blog and re do them.
VB.NET Classes and Objects
VB.NET is an Object Oriented programming language. The Objects referred to are created from something called a Class. You've already used Classes throughout this course. But we'll now have a closer look at them.
Object Oriented programming
The modern trend in programming languages is for code to be separated into chunks. When it's being used, each chunk of code (a chunk of code that opens text files, for example) is known as an Object. The code for the Object can then be reused whenever it is needed. Languages like C++ and Java are Object Oriented languages. Until Microsoft came out with VB.NET, the Visual Basic programming language was not OOP (object oriented programming). This time it is.
Object Oriented programming has a steeper learning curve, and things like Encapsulation, Inheritance and Polymorphism have to be digested. We're not going quite that far in this beginner's course. But you should have a good, basic understanding of just what Object are by the end of this section, and how to create your own Objects.
Classes and Objects
In VB.NET, a class is that chunk of code mentioned earlier. You've been using Classes all the time during this course. The Form you've started out with is a Class. If you look right at the top of the code window for a Form, you'll see:
Public Class Form1
The word "Public" means that other code can see it. Form1 is the name of the Class
If you look at the bottom of the coding window, you'll see End Class, signifying the end of the code for the Class.
When you place a Button or a textbox on the Form, you're really adding it to the Form Class.
When you start the Form, VB does something called instantiation. This basically means that your Form is being turned into an Object, and all the things needed for the creation of the Form are being set up for you (Your controls are being added, variables are being set up an initialised, etc).
And that's the basic difference between a Class and an Object: A Class is the code itself; the code becomes an Object when you start using it.
Object Oriented programming
The modern trend in programming languages is for code to be separated into chunks. When it's being used, each chunk of code (a chunk of code that opens text files, for example) is known as an Object. The code for the Object can then be reused whenever it is needed. Languages like C++ and Java are Object Oriented languages. Until Microsoft came out with VB.NET, the Visual Basic programming language was not OOP (object oriented programming). This time it is.
Object Oriented programming has a steeper learning curve, and things like Encapsulation, Inheritance and Polymorphism have to be digested. We're not going quite that far in this beginner's course. But you should have a good, basic understanding of just what Object are by the end of this section, and how to create your own Objects.
Classes and Objects
In VB.NET, a class is that chunk of code mentioned earlier. You've been using Classes all the time during this course. The Form you've started out with is a Class. If you look right at the top of the code window for a Form, you'll see:
Public Class Form1
The word "Public" means that other code can see it. Form1 is the name of the Class
If you look at the bottom of the coding window, you'll see End Class, signifying the end of the code for the Class.
When you place a Button or a textbox on the Form, you're really adding it to the Form Class.
When you start the Form, VB does something called instantiation. This basically means that your Form is being turned into an Object, and all the things needed for the creation of the Form are being set up for you (Your controls are being added, variables are being set up an initialised, etc).
And that's the basic difference between a Class and an Object: A Class is the code itself; the code becomes an Object when you start using it.
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