Character codes 4. Structure is a fundamental characteristic of computer software. The use of structuring permits decomposition of a large system into smaller, more manageable units with well-defined relationships to the other units in the system.
The most general form of system structure is the network. Node The nodes can represent processing elements that transform data and the arcs can be used to represent data links between nodes. Alternatively, the nodes can represent data stores and the arcs data transformation. Environment group templates Shared objects Processes 7.
Process Each process, one might find functional abstraction groups, data abstraction groups, and control abstraction groups. Template group Processing groups Utility group 8. Group Each group might consist of a visible specification part and a hidden body.
The visible portion would provide attributes such as procedure interfaces, data types, and data objects available for use by other groups. Visible part Static area Hidden part 9. Modular system include: i Well defined sub system ii Each abstraction single iii More than one major structure iv Function share global data v Function abstract data type Verification is a fundamental concept in software design.
Content Coupling: Content coupling occurs when one module modifies local data values or instructions in another module.
Common Coupling: Modules are bound together by global data structures. Control Coupling: Control coupling involves passing control flags as parameters or globals between modules so that one module controls the sequence of processing steps in another module. Stamp Coupling: Stamp coupling is similar to common coupling, except that global data items are shared selectively among routines that require the data.
Data Coupling: Data coupling involves the use of parameter lists to pass data items between routines. The most desirable form of coupling between modules is a combination of stamp and data coupling. Cohesion: The internal cohesion of a module is measured in terms of the strength of binding of elements within the module.
Coincidental Cohesion: Coincidental cohesion occurs when the elements within a module have no apparent relationship to one another. Logical Cohesion: Logical cohesion implies some relationship among the elements of the module. Ex: In a module that performs all input and output operations, or in a module that edits all data.
Naturally,my needs were a bit different and I had loads of questions. Before he sent me my pre-approval letter, he called to speak with me about what it meant and what could change. He made himself available to me at pretty much any hour via email and texts. He was very responsive and knowledgeable. I explained to him what my expectations were in terms of closing time and other particulars.
The more detailed design activities are conducted from the framework. Patterns A design pattern describes a design structure and that structure solves a particular design problem in a specified content.
Modularity A software is separately divided into name and addressable components. Sometime they are called as modules which integrate to satisfy the problem requirements. Modularity is the single attribute of a software that permits a program to be managed easily. Information hiding Modules must be specified and designed so that the information like algorithm and data presented in a module is not accessible for other modules not requiring that information. Functional independence The functional independence is the concept of separation and related to the concept of modularity, abstraction and information hiding.
The functional independence is accessed using two criteria i. Cohesion Cohesion is an extension of the information hiding concept. A cohesive module performs a single task and it requires a small interaction with the other components in other parts of the program. Coupling Coupling is an indication of interconnection between modules in a structure of software. Refinement Refinement is a top-down design approach. IEEE defines abstraction as 'a view of a problem that extracts the essential information relevant to a particular purpose and ignores the remainder of the information.
Functional abstraction : This involves the use of parameterized subprograms. Functional abstraction can be generalized as collections of subprograms referred to as 'groups'. Data abstraction : This involves specifying data that describes a data object. For example, the data object window encompasses a set of attributes window type, window dimension that describe the window object clearly.
Control abstraction : This states the desired effect, without stating the exact mechanism of control. The software architecture enables the software engineers to analyze the software design efficiently. In addition, it also helps them in decision-making and handling risks.
0コメント