Chapter 1 Software Development Dr. Bernard Chen Ph.D. University of Central Arkansas Fall 2008

Software Development Hardware: actual physical components (such as CPU, memory, hard drive…) Software: refers to programs used to control the operation of the hardware.

Software Development Software development is a complex process that is both an art and a science It is an art in that it requires a good deal of imagination, creativity, and ingenuity It is also a science that it uses certain standard techniques and methodologies

Software Development Phases Problem Analysis and Specification Design Coding Testing, Execution, and Debugging Maintenance

Software Development Model One of the earliest strategies for development software is known as the Waterfall Model

Waterfall Model

Realistic Waterfall Model

Software Development Phases Problem Analysis and Specification Design Coding Testing, Execution, and Debugging Maintenance

Problem Analysis and Specification Problem Analysis and Specification: The problem is analyzed and a specification for the problem is formulated For example: if we obtain a job request looks like:

Task Example Because of new government regulations, we must keep more accurate record of all students currently receiving financial aid and submit regular report to FFAO (Federal Financial Aid Office). Could we get the computer to do this for us???

Task Analysis Purpose Pre-condition (input): describe the state of processing before the program is executed Post-condition (output): describe the state of processing after the program is executed

Software Development Phases Problem Analysis and Specification Design Coding Testing, Execution, and Debugging Maintenance

Design Design: A plan for solving the problem is formulated Various design methods have been developed, two of major designs we describe here: top-down design and object-oriented design

Top-down design The original problem is partitioned into simpler subproblems For example, the problem we just had can be obviously divided into: 1. Get the student records 2. Process the records 3. Prepare the reports

One level partition

Two level partition

Three level partition

OOD:Object-Oriented Design Identify the objects in the problem's specification and their types. Identify the operations or tasks to manipulate the objects

Program=Algorithm + Data Structure Algorithm: “a step by step procedure for solving a problem or accomplishing some end” In computer science, algorithm must be: 1. Definite, unambiguous 2. Simple 3. Finite

Algorithms Unstructured goto's if-else's Structured while loop switch stmt

Software Development Phases Problem Analysis and Specification Design Coding Testing, Execution, and Debugging Maintenance

Coding There’s not much we can talk in coding, you all know what it is. After you select the language, three major principles you need to follow: 1. Programs and Subprograms should be well structured 2. All source code should be documented 3. It should be formatted in a style that enhances its readability

Software Development Phases Problem Analysis and Specification Design Coding Testing, Execution, and Debugging Maintenance

Testing, Execution, and Debugging Errors happen all the time!!! There are three different points at which errors can be introduced: 1. Syntax errors 2. Run-time errors 3. Logic errors

Different Kinds Of Tests Required Unit tests: Each individual program unit works? Program components tested in isolation Integration tests : Units combined correctly? Component interface and information flow tested System tests: Overall system works correctly? 25

The "V" Life Cycle Model

Two major types of testing Black box testing: Outputs produced for various inputs Checked for correctness Do not consider structure of program component itself. (so basically, it just test a lot of different inputs and match with the expected outputs )

Two major types of testing White box testing: examine code’s internal structure (Test for every loop, if statement, functions…) Test data is carefully selected

Software Development Phases Problem Analysis and Specification Design Coding Testing, Execution, and Debugging Maintenance

After the software has been used for several years, they will require modifications Studies show that a higher percentage of computing budgets and programmer time are devoted to software maintenance 1970s35-40% 1980s40-60% 1990s70-80% 2000s80-90%