Article Directory
1. Software
1. Definition of software
Software is not just a program, but a collection of
程序,数据, and what is needed to develop , use, and maintain a program所有文档
Program : A program is written to solve some specific problems and is
程序设计语言suitable for computer processing语句序列, designed and coded by developers
Documentation : Documentation is a record of software development activities, primarily for human reading. Documentation can be used not only for communication and exchange between developers and users, but also for the management of the software development process and the maintenance of the operation phase
2. Classification of software
From the perspective of computers 系统角度, it can be divided into two categories: system software and application software.
From the perspective of computers, 软件用途it can be divided into three categories: service, maintenance, and operation management.
3. The software crisis
3.1 The main problems of the software crisis
1. How to
开发meet the growing demands of multi-software
2. How to deal维护with the growing number of existing software
3.2 Causes of software crisis (6 points)
(1) Software is a logical component of a computer system, often with a large scale and complex structure
(2) The cost of software development continues to increase, and the maintenance cost rises rapidly
(3) The management of software development is difficult
(4) The technology of software development is backward
(5) Production Outdated methods
(6) Outdated development tools and slow production efficiency
Brief Note: Software is inherently complicated, and now it needs more money. Even if you have money, it is difficult to find suitable candidates for development process management. There is a three-piece set of objective obstacles (production technology, production methods, and production tools are backward)
2. Software Engineering
1. Definition of software engineering
Software engineering is a discipline that guides computer software
开发and维护工程学科software development and maintenance using engineering concepts, principles, technologies and methods
2. Software engineering goals (6 points)
(1) Reduce software development costs
(2) Meet all software functional requirements of customers
(3) Create software performance that meets customer requirements and satisfies users
(4) Has good ease of use, reusability and portability
( 5) Lower maintenance cost, higher reliability
(6) Complete the development tasks according to the contract requirements, and deliver them to customers within the specified period
Imagine running a software design company where you are the boss.
When starting a company, you must first lower the price before someone asks, and when you ask, you agree to all the software function requirements required by the user. Here, it is assumed that the customer requires to make a game.
It shouldn’t be too stuck after it’s done, the performance must go up. It’s not stuck, but if users want to launch this game on multiple platforms, the ease of use, reusability and portability must be good. After each platform is launched, it is impossible to have a team of maintenance personnel for each platform. High reliability is required, and finally, the development is completed according to the contract requirements, and it is delivered for use within the period stipulated in the contract (otherwise you will lose money if you breach the contract)
3. Contents of Software Engineering Research
软件开发技术The main research on software development methods, software development process, software development tools and technology
on 软件开发过程管理the main research software management and software engineering economics
4. Basic principles of software engineering (7 points)
(1) The development team should be fewer and more refined
(2) Adopt modern programming techniques
(3) Strictly manage with a staged life cycle
(4) Adhere to stage reviews
(5) Implement strict product control
(6) The results should be clear Review
(7) recognizes the need for continuous practice in software engineering
The basic principle can be understood as a brief design process.
First, build a team (fewer people and finer the best), then use modern programming technology (generally more mature), and
then strictly control according to the stages of the life cycle, and break down one by one. After each stage is written, it must be reviewed, and strict product control should be carried out. The results of the final review should be clearly visible. Finally, we must maintain a belief that software software engineering needs continuous practical improvement. Be open-minded and have more Change good technology, don't be too rigid
History of software engineering development (understand)
Program Design Era (1946~1956) //Ten Years
Program System Era (1956~1968) //Twelve Years
Software Engineering Era (1968~present)
5. Software life cycle
Meaning : It refers to the time when a certain software project is put forward and started to be implemented until the software stops using or is scrapped
Divide the software life cycle: Divide the life cycle into several stages, assign relative
独立(生存周期划分原则)tasks to each stage, each stage has technical review and management review, and test the development results of this stage from both technical and management aspects
The software life cycle is generally divided into three periods : software planning, software development, and software operation.
6. Software development model
Waterfall model: also known as life cycle model or linear sequence model , this model is a model that specifies the various activities of the software life cycle as several stages connected in a linear sequence, including problem definition, feasibility study, demand analysis, outline design, Detailed design, coding, testing, and maintenance are by far the most widely used process model , driven by documents, and suitable for software development projects with clear requirements
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Waterfall model features:
- The sequence and dependence of the stages : the work of the next stage must be completed after the work of the previous stage is completed, and the output document of the previous period is the input document of the latter stage
- The characteristics of deferred implementation : code implementation after sufficient preparation, separate logical design and physical design
- The viewpoint of quality assurance : ① The specified relevant documents must be completed in each stage ② The completed documents must be reviewed before the end of each stage
- Existing problems : It is an ideal linear development model, lacks flexibility, especially cannot solve the problem of unclear or inaccurate software requirements
Rapid prototyping model: first quickly establish a prototype system that can reflect the main needs of users, let users try it on the computer, and let users understand the overview of the future target system through practice, so as to judge which functions meet the needs and which aspects need to be improved. Development The personnel quickly modify the prototype system according to the user's opinion, and then ask the user to try again, so that iterative improvement, and finally establish a new system that fully meets the user's needs
Incremental model: also known as incremental model, software is developed "gradually" in the model, and software products are designed, coded, assembled and tested as a series of incremental components, which is a non-holistic development model . Each component is composed of multiple interacting models, and can complete some specific functional
characteristics : develop part, show part to users, so that users can see part of the software early in time, and find problems early
Spiral model: Adding the risk analysis neglected by the first two models, it makes up for the deficiencies of the two models. It is a risk-driven model
Fountain model: It is a typical object-oriented software development model , driven by the needs of users and driven by objects, suitable for object-oriented development methods
Comparison of each model:
| waterfall model | Classic, suitable for projects with little change in requirements |
|---|---|
| rapid prototyping model | Quickly obtain user needs |
| incremental model | Flexible, allowing software changes |
| spiral model | join the risk |
| fountain model | Typical object-oriented development model |
| component-based development model | Improve software reusability and usability |
| Unified Process Model | UML-based oo process model |
| Formal Model Based | ensure strict |
Comparison of traditional software engineering and object-oriented software engineering
Traditional software engineering is based on structured design language
What is object-oriented software engineering, and briefly describe the meaning of his practice and traditional software engineering : software engineering based on object-oriented programming
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Difference : traditional software is based on structured programming, while object-oriented software engineering It is based on object-oriented programming. Compared with the development idea of process-oriented software engineering, the object-oriented development method is no longer oriented by function division, but takes the object as the center of the whole problem analysis, and carries out the analysis and design work of the system facing the object.
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Contact : In terms of development process, object-oriented software engineering, like traditional software engineering, divides software development into several stages such as analysis, design, coding and testing, but the specific work of each stage is different. The traditional software development process includes requirements analysis, overall design, detailed design, process-oriented coding and testing; while the object-oriented software engineering development process includes requirements analysis and object extraction, detailed object design, object-oriented coding and testing