1.04- SDLC (1).pptx

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Software Design

Life Cycle

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Essential Standard

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1.04- Understand program design, analysis, and

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Purpose

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This lesson will review the Software Design Life Cycle and introduce debugging techniques used in C#. Many of

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Software Design Life Cycle

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A set of guidelines for writing software that satisfies the needs of others.

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Step 1

Analyze requirements

• Programmer meets with the client to talk about the requirements for the software

• Discuss the functionality and the user’s interface. • Discuss the goals of the project and timeline for

completed product or achieving other results.. • Reflect on the cultural needs of your environment

and identify means of helping.

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Design and Evaluation

• Programmer creates a conceptual design of the software

• Programmer makes sure that the design meets all the requirements determined by the client

Step

2

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Flowcharts

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As you learned in Programming I- flowcharts are used to produce a visual representation of your program.

Start/

End Decisio

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Flowchart Assignment

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Create a flowchart for the Tic-Tac-Toe program used in

1.02. Remember there are processes and decisions in this program.

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You can use:

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Visio- great diagramming tool from Microsoft.

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Word and PowerPoint also have flowcharting shapes built in

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Sample

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Implementation and Integration

• Programmer through the use of the IDE

(integrated development environment) codes the application or service.

• The IDE used in this course is Visual Studio.

Step

3

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Testing

• Client and programmer test the software to make sure that it operates without any bugs.

• This is a thorough test of the software. Testing will continue once the end user takes delivery of the product.

• Ensures that bugs or defects do not remain in the final product.

Step

4

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Debugging

Techniques

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Types of Errors

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Syntax

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Run Time (Exceptions)

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Logic

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Syntax Error

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A programming language speaks a “language” of its own using reserved words called keywords.

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A syntax error is an error in the use of a keyword, control character or other language function. The program will not run (compile) with a syntax error. Visual Studio calls syntax errors a “build error.”

Left: a common error for new C#

programmers

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Syntax Error Examples using

Variables

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integer x = 7;

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sting name = “John”;

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string age = 14;

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Syntax Error Examples using

Variables

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integer x = 7;

• Invalid keyword- use int in C#

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sting name = “John”;

• Mispelled string- sting is not a data type

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string age = 14;

• A numerical value cannot be placed in a string without placing it in quotes.

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int num = “apple”;

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Error List

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The Error List is a very useful in Visual Studio. All current syntax errors are listed.

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All errors listed must be corrected before the program can compile. Double click on an error to go to that line in

code.

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Run Time Errors

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Run time errors occur when the program encounters an exception it does not know how to handle.

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This will cause the program to crash (stop working).

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Run Time Error Examples

• Attempting to divide by zero (num1 / num2 where num2 is still set to its default value of 0 or otherwise assigned a value of 0)

• A user enters a string into a textbox meant for a numeric value. The run time error will occur when the program attempts to convert the bad data.

• The program attempts to assign a value to an array index value that does not exist.

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Logic Errors

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A logic error is an error is the thinking or logic of the coder. The program runs normally, but produces results different from the expected output.

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Logic Error Examples

• Endless loops- A loop whose run condition is always true

Example: while(x < 4) {

some code but forgetting to add x++

} //x will never be greater than 4 and this loop with run forever

• A loop or if statement using an improper comparison

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Logic Error Example

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int howMany = 12;

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for(i=0; i>howMany; i++)

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Handling Errors

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Syntax errors are fatal errors. The program will not compile and run until they are corrected. There is no

method for handling them in a running program because they will not occur.

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Using features of the code and IDE we can debug for logic errors and prevent run time errors from crashing our

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Handling Exceptions

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Just like in VB we can use Try/Catch to handle exceptions in our program.

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Instead of the exception causing a crash- the try/catch block “catches” the “thrown” exception and runs some code instead.

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Try Catch Syntax

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try

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{

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Code to try for possible exceptions

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}

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catch

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{

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Code to run if the try code throws an exception

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Example Using Try/Catch

• try

• {

• intAge = Convert.ToInt32(strTempAge); //or txtAge.Text

• }

• catch

• {

• MessageBox.Show(“Enter a number. The value you entered is invalid. ” + strTempAge)

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Handled vs Unhandled

Exception

Left: Try/Catch block was used Above: No try/catch block-

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Debugging Logic Errors

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IDE features such as breakpoints and the Locals window can help debug logic errors in your program. Below is an example of a breakpoint.

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Line Numbers

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Line numbers make debugging easier by allowing you to quickly reference what line of code you are working on.

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Turn on Locals Window

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When a program is running (Pressed F5 or clicked the Green Triangle) visit the Debug menu and the Windows submenu. The Locals Window is one of the options you can select.

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Locals Window

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Our Breakpoint

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New options exist when the program is paused at a breakpoint.

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Options

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Continue- Run the program as normal from where the program paused

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Step Into- Move the program one line forward into a coding block

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Step Out- Move the program out of the current coding block

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Step Over- skip the next coding block

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Practice

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Practice using breakpoints and the Locals window using one of the programs you wrote in 1.01 or 1.02- especially ones with an if statement or loop.

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Deployment

• Programmer delivers the product to the client. • This could include installation and/or

customization.

• Client continues testing the software and reports issues to the programmer.

Step

5

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Documentation and Maintenance

• Programmer creates… • Help documents

• User manuals • Tutorials

• Programmer provides maintenance for the

software as agreed upon by the client. This could include fixing bugs, adding new features, or

implementing on new or updated platforms.

Step 6

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Comments in C#

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Just like in Visual Basic it is extremely important to comment your code.

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This is especially true in team environments where more than one coder will be working on a project.

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C# provides 2 ways to comment:

• // can be used for a single line comment or in line after a coding statement

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Comment Examples

age = Convert.ToInt32(tempAge); //convert the string data to integer  Inline comment after a coding statement

// This program will check an age. This is a single line comment

/* This is a multi-line comment * J. Crompton

* Computer Programming II * August 4, 2015

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Conclusion

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In this lesson we reviewed the Software Design Lifecycle and looked at debugging and IDE options for debugging in more detail.