Introduction of software -: This design is a process to transform user requirement into some suitable form which helps the programmer in software coding and implementation. For assessing user requirement an SRS (software requirement specification) document is created where for coding and implementation there is a need of more specific and detailed requirement in software terms. The output of this process can directly be used into implementation in programming language.
Software Design Level -: There are three level available in software design. These are the
1-: Architectural Design -: This type design is the highest abstract version of the system.It identifies the software as a system with many components interacting with each other. At this level the designer get the idea of proposed solution domain.
2.-: High level Design -: The high level design breaks the single entity multiple component concept of architectural design into less abstracted view of sub system and modules and depicts their interaction with each other. High level design focuses on how the system along with all of its components can be implemented in form of modules. It recognizes modular structure of each sub system and their relation and interaction among each other.
3.-: Detailed Design -:Detailed design deals with the implementation part of what is seen as a system and its sub system in the previous two designs.It is more detailed towards modules and their implementations. It defines logical structure of each module and there interface to communicate with other modules.
Modularization -: It is a technique to divide a software system into multiple discrete and independent modules which are expected to be capable of carrying out task independently. this modules may work as basic construct for the entire software. Designers tend to design modules such that they can be executed and compiled separately and independently.
Modular design unintentionally follows the rule of divide and conquer problem solving strategy this is because there are many other benefits with the modular design of a software. There are some advantage of modularization..
- Smaller components are easier to maintain
- program can be divided based on functional aspects
- desired level of abstraction can be brought in the program
- components with high cohesion can be re used again
- concurrent execution can be made possible
- desired from security aspect
Concurrency -: All software are meant to be execute sequentially. By sequential execution we mean that the coded instruction will be executed one after another implying only one portion of program being activated at any given time. A software has multiple modules then only one of all the modules can be found active at any time execution.
In software design concurrency is implemented by splitting the software into multiple independent units of execution like modules and executing them in parallel. In other words concurrency provide capability to the software to execute more then one part of code in parallel to each other.
Coupling and Cohesion -: when a software program is modularized its task are divide into several modules based one some characteristics as we know modules are set of instruct put together in order to achieve some tasks they are though considered as a single entity but may refer to each other to work together. There are measures by which the quality of a design of modules and their interaction among them can be measured. These measures are called coupling and cohesion.
Cohesion -: It is a measure that defines the degree of intra-dependability within element of a module.The greater the cohesion the better is the program design. There are several type cohesion available these are the ..
- Co-incidental cohesion -: It is unplanned and random cohesion which might be the result of breaking the program into smaller modules for the sake of modularization because it is unplanned. It may serve confusion to the programmers and is generally not accepted.
- Logical cohesion-: when logically cohesion categorized elements are put together into a module it is called logical cohesion.
- Emporal cohesion -: When elements of module are organized such that they are processed at a similar point of time it is called temporal cohesion
- procedural cohesion -when element of module are organized such that they are processed at a similar point of time it is called temporal cohesion.
- communication cohesion -: when elements of module are grouped together which executed sequentially and work on same data. It is called communication cohesion.
- Sequential cohesion- when element of module are grouped because thee output of one element serves as input to another and so on it is called sequential cohesion.
- Function Cohesion-: It is considered to be the highest degree of cohesion and it is highly expected. element of module in functional cohesion are grouped because they all contribute to a single well defined function. It can also be reused.
Coupling-: It is a measure that defines the level of inter dependability among modules of a program. It tells at what level the modules interfere and interact with each other. The lower the coupling the better the program. There are some coupling level
- Content coupling – when a module can directly access or modify or refer to the content of another module. It is called content coupling.
- common coupling-: when multiple modules have read and write access to some global data it is called common level coupling.
- control coupling-: Two modules are called control coupled if one of them decides the function of the other module or change its flow of execution.
- stamp coupling-: when multiple module share common data structure and work on different part of it, It is called stamp level coupling
- Data coupling -: Data coupling is when two module interact with each other by means of passing data. If a module passes data structure as parameter then the receiving module should use all its component.
Design verification -: The output of software design process is design documentation pseudo codes detailed, logic diagram process diagram and detailed description of all functional on non functional requirements. Which is the implementation of software depends on all outputs mention above.