Introduction to Application Development (chapter 2)

Introduction to Application Development : 

Introduction to Application Development

System Development Tools and Techniques : 

System Development Tools and Techniques

Modeling : 

Modeling Produces a graphical representation of a concept or process that systems developer can analyze, test and modify

Prototyping : 

Prototyping IT tests system concepts and provides an opportunity to examine input, output and user interface before initial decisions are made. A prototype is an early working version of an information system.

Computer Aided Systems Engineering Tools (CASE) : 

Computer Aided Systems Engineering Tools (CASE) Also called computer aided software engineering, is a technique that uses powerful software to help system analysts develop and maintain information system. It provides an overall framework for systems development and support a wide variety of design methodologies, including structured analysis and O-O analysis.

System Development Methods: : 

System Development Methods:

Structured Analysis: : 

Structured Analysis: Is a traditional systems development technique that is time tested and easy to understand. It uses a series of phases called SDLC (System development life cycle) to plan, analyze, design, implement and support an IS. IT users a set of process models to describe a system graphically.

Object – Oriented Analysis : 

Object – Oriented Analysis Combines data and the processes that act on the data into things called objects. System analysts used O-O to model real – world business processes and operations. As system analysts uses this model, its result is a set of software objects that represent actual people things, transactions, and events.

Joint Application Development and Rapid Application Development : 

Joint Application Development and Rapid Application Development JAD and RAD are both team based System Development Methods which either follows one phase of development process or more like a compressed version of the entire process.

Software Development Life Cycle : 

Software Development Life Cycle

Software Development Life Cycle : 

Software Development Life Cycle Also known as SDLC. The process of developing the application software.

SDLC Consists of six steps: : 

SDLC Consists of six steps: Problem Definition/ Program analysis Program Design Coding Testing Documentation Maintenance

Problem Definition/ Program Analysis : 

Problem Definition/ Program Analysis First Step:

Defining the problem: : 

Defining the problem: Also known as the program analysis, involves the following six tasks: Specifying the objectives of the program Specifying the outputs Specifying the input requirements Specifying the feasibility of the program Documenting the program analysis Specifying the processing requirements

Program Design : 

Program Design Second Step:

Program Design : 

Program Design The second phase of the SDLC. It consists of designing a solution.

Structured Program Design: : 

Structured Program Design: is a method of designing a computer program in such a way so as to minimize the complexity. Among the tool used in this stage are: Top down program design Flowcharts Pseudocode

Top Down Program Design: : 

Top Down Program Design: Is a structured design technique, in which the programmer having determined the outputs to be produced and the inputs required, identifies the major processing steps that the program must perform. These major processing steps are called Program Modules.

Top down design has some rigid rules: : 

Top down design has some rigid rules: Each module can have only one entry point and one exit point, so that the logic flow of the program is easy to follow. When the program is executed, it must be able to move from one module to the next in sequence, until the last module has been executed. each module should be different and should have a single function. Each module should be manageable size, in order to make the design and testing of the program easier.

Flowcharts: : 

Flowcharts: One of the widely used devices for designing programs, which graphically represents the logic needed to solve a programming problem. It represents the detailed sequence of steps, needed to solve the problem. They are frequently used to visualize the logic and steps in processing.

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Sample Symbols:

Pseudocode: : 

Pseudocode: An alternative or a supplement to flowcharts. It is a narrative rather than a graphical form of describing structured program logic. It allows the program designer to focus on the logic of the program and not on the details of programming or flowcharting.

Documenting the program design: : 

Documenting the program design: At the end of the program design stage, a formal document should be prepared to guide the future users.

Coding : 

Coding Third Step:

Coding: : 

Coding: Writing the program. In this step, you use the logic you develop in the program design stage to actually write the program.

Here are some of the qualities of a good program: : 

Here are some of the qualities of a good program: It should be easily readable and understandable by people other than the original programmer. This is accomplished by including comments within a program. It should be efficient, increasing the programmer’s productivity.

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It should not take excessive time to process, or occupy any more computer memory than necessary. It should be reliable, able to work under all reasonable conditions, and always get the correct output.

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It should be to detect unreasonable or error conditions and indicate them to the programmer or user without stopping all operations – crashing the system. It should be easy to maintain and support after the installation.

Three Factors that make programs efficient are: : 

Three Factors that make programs efficient are: The statements can be arranged into patterns that enhance readability. The variables – they are symbolically named entities to which values are assigned – used are carefully and descriptively named. Comments can be inserted into the program to document the logic patterns and program flow.

Testing : 

Testing Fourth Step:

Testing the program: : 

Testing the program: This means running the program and fixing if it does not work, or debugging it. There are two types of bugs or errors: Syntax errors Logic errors

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Syntax errors – is a violation of the rules of whatever programming language the programmer is writing in. Logic error – Is when programmer has used an incorrect calculation or left out a programming procedure.

Documentation : 

Documentation Fifth Step:

Documenting the program : 

Documenting the program Program documentation – is a process that starts from the first phase of the development life cycle.

Final Document should contain the following information: : 

Final Document should contain the following information: Program analysis document, with a concise statement of the program’s objectives, outputs, inputs and processing procedures. Program Design document, with detailed flowcharts to appropriate diagrams. Program verification document, outlining the checking, testing and correction procedures along with a list of test data and results. log used to document future program revision and maintenance activity.

Maintenance : 

Maintenance Sixth Step:

Maintaining the program: : 

Maintaining the program: - a program after it has been fully tested and became operational, it will require maintenance to modify or update it. - Once software is supposedly working, it is commonly believed that maintenance is minimal and can be handled by programmers on catch as catch can basis.