Overview of Program Design

Steps in program development

The steps in program design are similar to the steps in problem solving. They are:

1. Define the problem

2. Outline the solution

3. Develop the outline into an algorithm

4. Test the algorithm for correctness

5. Code the algorithm into a specific programming language

6. Run the program on the computer

7. Document and maintain the program

Define the Problem

You need to understand the problem before you can expect to get a correct solution to the problem. What information (inputs), is given to you to use to solve the problem? What will the solution (outputs) of the problem, look like? What calculations (processes), will be used to change the input information into the desired output?

Outline the Solution

Break the problem into the steps of what must be done to solve the problem. List what tasks need to be done to solve the problem. An English outline is a good tool for doing the job.

Develop the outline into an algorithm

Expand the outline from the previous step into a complete solution. It should list all the steps that need to be done, in the correct order they need to be done in.

Test the Algorithm for Correctness

In this step, you pretend to be a computer and execute the steps in the algorithm. This is called "Desk Checking." Be care to follow the algorithm exactly! Don't add steps, or leave out any steps. Don't rearrange the steps. If you don't get the right answer to the problem, then you have an error in the algorithm. Fix it and try again until you get the right answer

Code the Algorithm into a Specific Programming Language

Once the algorithm, or complete outline works correctly, you need to translate the algorithm into a computer language that your computer undrstands. This is only 5 to 10% of the total programming process!

Run the Program on the Computer

Now, enter the program into the computer's memory, enter the input data, and hve the computer execute the program. If you get the correct answer to the problem, the program works! Otherwise, look for errors in the program and try again.

Document and maintain the program

Warning! The Documentation of the program started by writing down "What is the Problem!" It continues through each step of the design process.

Once the program works correctly, you want make sure the documentation is up to date and be ready to maintain the program. Good programs get better during the life-time as people think of better way to do things and additional taks the program might do. Up to data documentation is very important!

Program design methodology

The fundamental principle of program design is based on the fact that a program accepts input data, processes that data, and then delivers that data to the program user as output.

Here are some common design approaches:

procedure-driven

event-driven

data-driven

structured programming

Procedure-driven program design

The procedure-driven design is bases on the idea that the most important feature of a program is 'what' it does.

Event-driven program design

The event-driven program design is based on the idea that an event or interaction with the outside world can cause a program to change from one known state to another.

Data-driven program design

The data-driven program design is based on the idea that the data in a program is more stable than the processes involved.

Procedural versus object-oriented programming

Procedural programming is based on a structured, top-down approach to writing effective programs

The approach concentrates

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