Introduction to software engineering

Software
Program + file + data
Software function classification
1） Systems software ： Closely cooperate with computer hardware to coordinate all computer components with relevant software and data 、 Software that works efficiently . Such as operating system 、 Compiler, etc .
2） Support software ： Instrumental software to assist users in developing software .
3） Application software
Software engineering definition
Systematize 、 Normalization 、 A measurable approach to software development 、 During operation and maintenance ; Study the way to realize it
Software life cycle

1. Feasibility study and plan ： What is the solution to the problem ？ There are workable solutions ？ Rough plan
2. Demand analysis ： What must the target system do ？ The demand analysis of the feasibility study is rough 、 inaccurate ; Requirements analysis is complete 、 accurate : indeed 、 Clear 、 Specifically .
3. overall design ： How to achieve the target system ？ Analyze and recommend the best scheme according to the demand design scheme ; Design software structure, etc .
4. Detailed design ： How to implement the system ？ Design the algorithm and data structure of each module .
5. Realization （ Coding and unit testing )： Choice language 、 Tool translation detailed design results 、 Test module .
6. Integration testing ： Assemble the unit tested modules for testing , Make the software meet the predetermined requirements through testing .
7. Confirmation test ： The user shall test according to the requirements and specifications
8. Use and maintenance ： Through necessary maintenance activities, the system can meet user requirements for a long time .

Corrective maintenance ： Errors found during software operation , For maintenance .
Adaptive maintenance ： Changes in software and hardware environment during software operation , Maintenance performed
Integrity maintenance ： Users need to improve or expand the software , Maintenance performed
Preventive maintenance ： Prepare for future maintenance .
Common software process models

Waterfall model
1. Phases are sequential and dependent ： The previous stage ends and the next stage begins , Output documents in the previous stage , Input documents in the latter stage .
2. Postpone the realization of ideas ： Waterfall model sets up system analysis before coding 、 The system design , Postpone the physical implementation of the program , Ensure solid preliminary work .
3. Quality assurance point of view ： The waterfall model adheres to two important practices at each stage : First, each stage must be completed completely 、 Accurate documentation . Communication between personnel during software development 、 Important basis for maintenance during operation . Second, review the documents before the end of each stage .
advantage ：
Improve software quality , Reduce maintenance costs , Ease the software crisis .
shortcoming ：
The model lacks flexibility , Can't solve the problem of unclear demand . It is impractical for users to put forward complete and accurate requirements without practice .
Rapid prototyping model
Quickly establish a prototype system that reflects the main needs of users , Users evaluate and revise the requirements repeatedly , Develop the final product .
advantage ：
Determine that the demand is better than the waterfall model （ Interact with users through prototypes ）; Provide learning tools , Through developing prototypes and demonstrating prototypes, it has a positive effect on developers and users to understand the system ; Some software prototypes can become part of the final product .
shortcoming ：
The rapid establishment of the system structure and continuous modification may lead to low product quality, and the internal structure of the prototype system may be poor .
Incremental model
Also known as incremental model , When developing software, the software product is designed as a series of incremental components 、 code 、 Integration and testing . Different from waterfalls and rapid prototyping models ： Waterfall and rapid prototyping model is to submit products that meet all requirements to users at one time . Incremental model is to submit products to users in batches .
advantage ：
Submit useful work products to users in a short time ; Users have plenty of time to learn to adapt to the product ; The software structure must be open , It is convenient to add new components to existing products .
shortcoming ：
It is difficult to achieve the third advantage .
Spiral model
Fountain model
Rational Unified process
Microsoft software development process