Software:

In our day to day life ,we often come across the word 'software' knowingly or unknowingly, maybe we know or don't know the meaning of it. Many of our older generation use this word related to computer course or degree which his or her son,daughter other relatives are pursuing.So they take for granted that software is just related to computers and is an educational field and most important a source to earn a great amount of money.

Now lets get over this and the question arises what actually is a software???.An expert will say that "its a collection of programs of various types that is used to operate on computers and its integrated devices to achieve specific results by taking in inputs and producing suitable outputs." In layman's language it can be defined as a set of instructions or commands designed by a person(programmer) given to computer to perform some work or they are the set of steps that are used to perform some activity that is needed by the user.

As we have got classification in almost all the products things etc,we too have classification in softwares.Softwares can broadly be classified into 4 main categories which are as follows::

• 1>>Application software: these are the softwares or programmes which are related to particular applications or they themselves are application.In other words they are directly related to the end users who will use them depending on their will.examples of these softwares are any browser say firefox,opera,safari etc

• 2>>System software: these are the softwares that are directly related to the operating systems and they in general supports the application softwares.Basically these softwares provide the necessary framework by which user communicate with the computer's memory and commands.example you can say is of any operating system.
• 3>>Web application softwares::Previously these types of softwares were considered same as application softwares.But with the rapid growth of internet technology there is need to consider these softwares as a different field.in this field all aplications are related to internet and connectivity or plainly you can say a networking field.examples are browsers,web servers etc
  • • 4>>Middleware services(softwares)::these are the softwares that in turn provides the job of servicing one entity to other.In general these are the mediators that serves as a medium for two different softwares to communicate. examples of this are CORBA etc or you can say sending email from one o.s to another o.s(the service which does this job is middleware services).
    • Now after categorising softwares,there is an alternate way by which you can term or label a software,i.e by saying *
    • Freeware::which means this softwares are free to use but they have restrictions on their copyrights,so you cannot sell them *
    • Shareware::Now softwares which have trial periods and after which you have to buy them generally come under this category. *
    • Open source:: Here the source code of the software is provided freely and you can modify the software to another and have the rights to sell this softwares.
    • * Liteware :: this are the softwares which are just like demo versions with some advanced features disabled. In this way, this was the brief introducation about softwares.
    • Following are some of the links for free softwares
    • www.softpedia.com
    • www.source-forge.net
    • www.download.com
    • www.brothersoft.com

A software before comes to market undergoes several number of stages. These series of stages that a s/w product undergoes during its lifetime is called software life cycle. There are different models for descriptive and diagrammatic representation of software life cycle. The life cycle model forms a common understanding among the s/w engineers. It helps to develop s/w in a systematic and disciplined way.

Proper documentation of the life cycle model is a mandatory requirement for quality assurance. By documentation, inconsistencies, redundancies and omission in the development process can be identified easily. It also enhances the understanding of process among the developers. So, In each satge of development, everything is written in script format for future reference purpose.

Waterfall Model:
This model divides the life cycle into number of phases. The different phases are as follows:
1)    Feasibility study
2)    Requirement analysis and specification
3)    Design
4)    Coding and unit testing
5)    Integration and system testing
6)    Maintenance

Among all the phases, the maintenance phase requires the maximum effort. Each phase has well-defined starting and ending criteria which is documented. And it requires different amounts of effort for each phase.

1) Feasibility study:

The main aim of feasibility study is to determine financial and technical feasibility to develop the product. It involves properly analyzing the problem. Collecting relevant information related to the product like required input data, the processing required and the output data required.

Different alternative solution strategies are compared for project development. In this stage the project can be abandoned if it is not feasible because of high cost, resource constraints or technical problems.

2) Requirement analysis and specification:

The goal of this stage is to understand the exact requirements of the customers. For this interviews and discussions are conducted with the customers. Any ambiguity or contradiction in the requirements must be resolved before proceeding further.

Finally, all the user requirements are systematically organized into a Software Requirements Specifications (SRS) document. This document is reviewed and approved by the customer. It also serves as a contract between the developers and the customer

3) Design:

In this phase the requirements specified in the SRS document are given a structure that can be implemented in programming language. In other words the software architecture is developed.

In traditional design approach the different functions to be supported by the system and the data flow among them are identified. All these information are represented diagrammatically in Data flow diagrams (DFD). Then the system is decomposed into modules. The data structure and algorithms of each module are also designed in this stage.

4) Coding and Unit Testing:

The goal of this stage is to translate the software design into source code. Each component of the design is implemented as a program module. The programming can be done using any language like C, C++, Java according to the project requirement.

In this stage each module is tested separately to ensure correct working of all individual modules. Unit testing is done when a module has been coded and successfully reviewed.

5) Integration and system testing:

In this phase all the modules are integrated in a planned manner. The partially integrated system is tested and a set of previously planned modules are attached to it. At last system testing is carried out when all the modules have been successfully integrated.

System testing ensures that the system conforms to all the user requirements specified in SRS document. Generally it consists of 3 kinds of activities.
α – testing is performed by the software development team. β - testing is performed by a friendly set of customers and acceptance testing  is performed by the customer after product delivery.

6) Maintenance:

A software product needs to be maintained to correct errors, enhance features or upgrade to a new platform. It requires much more effort than the effort necessary to develop the product.