[frameworks] What is a software framework?

Can someone please explain me what a software framework is? Why do we need a framework? What does a framework do to make programming easier?

Beyond definitions, which are sometimes understandable only if you already understand, an example helped me.

I think I got a glimmer of understanding when loooking at sorting a list in .Net; an example of a framework providing a functionality that's tailored by user code providing specific functionality. Take List.Sort(IComparer). The sort algorithm, which resides in the .Net framework in the Sort method, needs to do a series of compares; does object A come before or after object B? But Sort itself has no clue how to do the compare; only the type being sorted knows that. You couldn't write a comparison sort algorithm that can be reused by many users and anticipate all the various types you'd be called upon to sort. You've got to leave that bit of work up to the user itself. So here, sort, aka the framework, calls back to a method in the user code, the type being sorted so it can do the compare. (Or a delegate can be used; same point.)

Did I get this right?

A framework helps us about using the "already created", a metaphore can be like,

think that earth material is the programming language,

and for example "a camera" is the program, and you decided to create a notebook. You don't need to recreate the camera everytime, you just use the earth framework (for example to a technology store) take the camera and integrate it to your notebook.

Technically, you don't need a framework. If you're making a really really simple site (think of the web back in 1992), you can just do it all with hard-coded HTML and some CSS.

And if you want to make a modern webapp, you don't actually need to use a framework for that, either.

You can instead choose to write all of the logic you need yourself, every time. You can write your own data-persistence/storage layer, or - if you're too busy - just write custom SQL for every single database access. You can write your own authentication and session handling layers. And your own template rending logic. And your own exception-handling logic. And your own security functions. And your own unit test framework to make sure it all works fine. And your own... [goes on for quite a long time]

Then again, if you do use a framework, you'll be able to benefit from the good, usually peer-reviewed and very well tested work of dozens if not hundreds of other developers, who may well be better than you. You'll get to build what you want rapidly, without having to spend time building or worrying too much about the infrastructure items listed above.

You can get more done in less time, and know that the framework code you're using or extending is very likely to be done better than you doing it all yourself.

And the cost of this? Investing some time learning the framework. But - as virtually every web dev out there will attest - it's definitely worth the time spent learning to get massive (really, massive) benefits from using whatever framework you choose.

A framework provides functionalities/solution to the particular problem area.
Definition from wiki:

A software framework, in computer programming, is an abstraction in which common code providing generic functionality can be selectively overridden or specialized by user code providing specific functionality. Frameworks are a special case of software libraries in that they are reusable abstractions of code wrapped in a well-defined Application programming interface (API), yet they contain some key distinguishing features that separate them from normal libraries.

A lot of good answers already, but let me see if I can give you another viewpoint.

Simplifying things by quite a bit, you can view a framework as an application that is complete except for the actual functionality. You plug in the functionality and PRESTO! you have an application.

Consider, say, a GUI framework. The framework contains everything you need to make an application. Indeed you can often trivially make a minimal application with very few lines of source that does absolutely nothing -- but it does give you window management, sub-window management, menus, button bars, etc. That's the framework side of things. By adding your application functionality and "plugging it in" to the right places in the framework you turn this empty app that does nothing more than window management, etc. into a real, full-blown application.

There are similar types of frameworks for web apps, for server-side apps, etc. In each case the framework provides the bulk of the tedious, repetitive code (hopefully) while you provide the actual problem domain functionality. (This is the ideal. In reality, of course, the success of the framework is highly variable.)

I stress again that this is the simplified view of what a framework is. I'm not using scary terms like "Inversion of Control" and the like although most frameworks have such scary concepts built-in. Since you're a beginner, I thought I'd spare you the jargon and go with an easy simile.

In General, A frame Work is real or Conceptual structure of intended to serve as a support or Guide for the building some thing that expands the structure into something useful...

at the lowest level, a framework is an environment, where you are given a set of tools to work with

this tools come in the form of libraries, configuration files, etc.

this so-called "environment" provides you with the basic setup (error reportings, log files, language settings, etc)...which can be modified,extended and built upon.

People actually do not need frameworks, it's just a matter of wanting to save time, and others just a matter of personal preferences.

People will justify that with a framework, you don't have to code from scratch. But those are just people confusing libraries with frameworks.

I'm not being biased here, I am actually using a framework right now.

The summary at Wikipedia (Software Framework) (first google hit btw) explains it quite well:

A software framework, in computer programming, is an abstraction in which common code providing generic functionality can be selectively overridden or specialized by user code providing specific functionality. Frameworks are a special case of software libraries in that they are reusable abstractions of code wrapped in a well-defined Application programming interface (API), yet they contain some key distinguishing features that separate them from normal libraries.

Software frameworks have these distinguishing features that separate them from libraries or normal user applications:

1. inversion of control - In a framework, unlike in libraries or normal user applications, the overall program's flow of control is not dictated by the caller, but by the framework.[1]
2. default behavior - A framework has a default behavior. This default behavior must actually be some useful behavior and not a series of no-ops.
3. extensibility - A framework can be extended by the user usually by selective overriding or specialized by user code providing specific functionality.
4. non-modifiable framework code - The framework code, in general, is not allowed to be modified. Users can extend the framework, but not modify its code.

You may "need" it because it may provide you with a great shortcut when developing applications, since it contains lots of already written and tested functionality. The reason is quite similar to the reason we use software libraries.

I'm very late to answer it. But, I would like to share one example, which I only thought of today. If I told you to cut a piece of paper with dimensions 5m by 5m, then surely you would do that. But suppose I ask you to cut 1000 pieces of paper of the same dimensions. In this case, you won't do the measuring 1000 times; obviously, you would make a frame of 5m by 5m, and then with the help of it you would be able to cut 1000 pieces of paper in less time. So, what you did was make a framework which would do a specific type of task. Instead of performing the same type of task again and again for the same type of applications, you create a framework having all those facilities together in one nice packet, hence providing the abstraction for your application and more importantly many applications.

A framework has some functions that you may need. you maybe need some sort of arrays that have inbuilt sorting mechanisms. Or maybe you need a window where you want to place some controls, all that you can find in a framework. it's a kind of WORK that spans a FRAME around your own work.

EDIT: OK I m about to dig what you guys were trying to tell me ;) you perhaps havent noticed the information between the lines "WORK that spans a FRAME around ..." before this is getting fallen deeper n deeper. I try to give a floor to it hoping you're gracfully:
a good explanation to the question "Difference between a Library and a Framework" I found here
http://ifacethoughts.net/2007/06/04/difference-between-a-library-and-a-framework/

I'm not sure there's a clear-cut definition of "framework". Sometimes a large set of libraries is called a framework, but I think the typical use of the word is closer to the definition aioobe brought.

This very nice article sums up the difference between just a set of libraries and a framework:

A framework can be defined as a set of libraries that say “Don’t call us, we’ll call you.”

How does a framework help you? Because instead of writing something from scratch, you basically just extend a given, working application. You get a lot of productivity this way - sometimes the resulting application can be far more elaborate than you could have done on your own in the same time frame - but you usually trade in a lot of flexibility.

A simple explanation is: A framework is a scaffold that you can you build applications around.

A framework generally provides some base functionality which you can use and extend to make more complex applications from, there are frameworks for all sorts of things. Microsofts MVC framework is a good example of this. It provides everything you need to get off the ground building website using the MVC pattern, it handles web requests, routes and the like. All you have to do is implement "Controllers" and provide "Views" which are two constructs defined by the MVC framework. The MVC framework then handles calling your controllers and rendering your views.

Perhaps not the best wording but I hope it helps