The term iterative means over and over again, as in repetition.

The term stepwise means in stages, as in going up the stairs step by step.

The term refinement means slowly progressing, as in towards a goal.

Refined sugar is sugar from which "impurities" are removed.

Sports teams refine their techniques as the season progresses.

What is stepwise refinement in terms of solution implementation? Give a specific example in terms of computer program implementation.

Programs are designed using systems analysis and design techniques.

Choices:

• Do the whole project and see if it works (hundreds of millions of dollars).
• Do it in stages and make a decision at each stage (reduce risk).

First iteration: develop a working prototype

Automate the entire process so you can come back to it.

UML (Unified Modeling Language) is an object-oriented visual modeling language for systems design, analysis, and implementation.

An OOP (Object Oriented Programming) language is useful for use with UML.

• Java
• .NET (not the previous Visual Basic)

Program are implemented using iterative stepwise refinement.

• iterative means in stages, one stage after the other
• refinement means each stage gets more refined

Wrong way: Type a lot of text into a program and then try to get it working.

Is this how many beginning programmers start a program?

Do they then expect to get help using a bad programming methodology?

Right way: Start with a minimal working program, add little pieces of code, in stages, such that after each small change, the program still compiles and does something. Each stage gets closer to the final working program.

This works from programs of a few lines to programs consisting of thousands of pages of code.

It is a very scalable way to program.

What happens if you come to me with a large piece of code that does not work?

If you come to me with a large piece of code that does not work, I will ask to see the most recent version that did work.

I will usually ask you to go back to that previous version and work from there until you find the problem.

That's what I do. That's what most programmers do. You should not use techniques that do not work well and that most programmers do not use. One way to iteratively refine your program is as follows.

• Include a digit, starting at "1", at the end of a program name.
• Use the "Copy to new program" option, using the next digit in the sequence, for the next iteration of your program.

That way, you can easily go back to a previous version.

A sophisticated version control system will manage this for you. In a simple system, you need to manage this.

What is Microsoft's version control system?

Microsoft's version control system is Visual SourceSafe.

• Let's you roll back to a previous version.
• Programmers check-out and check-in code.

Why is iterative refinement used?

Otherwise, you can spend/waste a lot of time trying to get a program working.

Programs are not typed in from beginning to end. Programs are developed in stages.

An artistic masterpiece is not painted from upper left to lower right.

A program is not to be read from top to bottom, textually.

A build is a compilation of the software system that results in an executable program.

A compiler compiles one piece of code (in a file) from source code to object code.

A build compiles many pieces of code (in many files) from source code to object code, and links them together such that the entire software system can be run.

Most "Help", "About" screens show the build number.

Usually, an IDE (Integrated Development Environment) will have an option to automatically increment the build number every time that the project is compiled.

To keep projects from getting bogged down, Microsoft uses daily builds.

The daily build attempts to minimize the problems of getting a large amount of code working. It was working yesterday, so it should work today. Windows 2000 was a few years late, but build 2195 being sent to manufacturing in December, 1999. Microsoft likes to have at least one build done every working day, for their sync and stabilize software development strategy, so this took a few years.

No one wants their code to "break" the build.

If your part of project causes the build to fail, or not work properly, you usually get to stay late that day.

Briefly explain the Microsoft sync and stabilize approach to software development and how it compares to an iterative and incremental software development process.