How to design a project ( detail ) ?? indetail [closed]

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My question is really very important . When i program i have seen that i had lots of errors in programming logic + structure + a f开发者_StackOverflowlexible when it goes for testing , i have read many books on OOPS and my all the concept are clear but i do not know where to start design of my code or project . can any body help me how to improve this part of programming skill.

although i work on php+javascript but this question is for all the programmers on stackoverflow

note- usually when i hold paper and pen i think where to start from .. if i make something problem is how to simplyfy.... and many others which u all are facing / faced

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Well, I think everyone is different as is every project. But here is what I personally do...

For my own projects, i.e. no client requirements, I start at one end or the other, either with the database structure or the UI. I then work down through the layers making sure that I maintain clear separation of concerns to make testing (unit and system) as well as maintenance as easy as possible.

One thing to note is that regardless of your approach I think the process is iterative. I will often work, refactor, work, refactor etc so don't get too bogged down with the details and feel you have to stick to them. The requirements are the key thing (whether for yourself or for a client), the technical implementation is largely irrespective.

When dealing with clients the process is somewhat different. You will need to do a fair amount of design up front so again think from one layer to the next trying to keep as much of the logic in the correct layers as possible. As an example you have your DB, then you want a data access layer (DAL) to abstract your code from the DB access. Then you want specific business logic libraries which use the DAL, this abstracts the higher portions of code from the data (they go through the business layer) etc etc.

Just think of each level and try and keep it as generic as possible, that way when you wish to change the storage for the data, you simply change the DAL and everything else works as before...

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As far as starting a design of your project is concerned, whole lot depends on what you are developing, that is requirement of the application. So first thing is that you must collect information about the purpose of your application. And when we start to program, a plain trend must be kept in mind, which is, as a universal fact of programming, Input-Process-Output. So, design starts with input. Just collect as much information as you can about what will be required as your input of application. If the input is not made by your user, than it is not required to be mentioned in your front-end design (In Windows language, the so called "Form"). What user will give, is matter of concern in designing the input area (very first step to start project).

During the designing phase, constant interaction is required with user to make effective & flexible start design, as ultimately he/she is going to use. If I'm starting a project's designing, I always consider the user a lazy person, if we keep that thing in mind, our application will be simpler & easy to use. Once, you'll kick-off the start, its just a flow, that'll suggest you next step.

Hope this helps............. :-)