two,
1, explain the concept of a software life cycle and to provide an example to explain its various stages, including production and delivery (not limited to the waterfall model life cycle)
Software life cycle:
Software life cycle, also known as the software life cycle or system development life cycle, until retirement is to produce software life cycle, there are problems within the defined period, feasibility analysis, general description, system design, coding, debugging and testing, acceptance and operation maintenance and other upgrades to the waste stage, this time by split-range thinking is an ideological principles of software engineering, that is, step by step, step by step, each stage must have defined, work, review, documented for exchange or for future reference, in order to improve the quality of software. But with the maturity of the new object-oriented design methods and techniques, design guidance method of the software life cycle is gradually reduced.
Each cycle has a definite life cycle tasks, and produce a certain specification documents (information) submitted to the next cycle as a basis for continued work. According to the software life cycle, software development is no longer just simply stressed that "coding", but summed up the whole process of software development. Software engineering requirements can only be the beginning of each cycle work must be the result of the previous cycle to establish "correct" continue on the premise; therefore, each cycle is press the "Activities - Results - Audit - reactivation - right until the result is" loop reciprocating progress.
The various stages of the life cycle of iterative model:
In most traditional life cycle, the stage is named after one of the main activities: requirements analysis, design, coding, testing. Serial traditional software development process emphasize the implementation of most of the work, an activity that is required to start after the completion of the previous activity, take off clothes over to form a string, the string on the formation process of the life cycle of a software project. In an iterative model, each stage will perform a traditional, full string of a serial process, a process execution string is the first iteration. Each iteration process includes all activities involved in different proportions.
The requirements analysis phase : In the case of software development is determined feasible, the various functions of the software need to implement detailed analysis. Requirements analysis phase is a very important stage, and is constantly changing and advanced stage in the entire software development process, can lay a good foundation for the success of the entire software development projects.
Software design stage (outline design and detailed design): mainly based on the results of the needs analysis, the entire software system design, system framework design, database design, and so on. Software coding phase: the result is converted into the program code of software designed to run a computer. We must develop a unified coding in the program, in line with the preparation of specifications standards. In order to ensure the program's readability, maintainability, improve the efficiency of the program.
Software testing phase : After the completion of the design software to go through rigorous testing to detect the presence of software throughout the design process and correct the problem.
Software operation and maintenance phase : the software life cycle is the longest stage, including corrective maintenance and improve maintenance aspects
Production delivery phases: the purpose of the delivery phase of the software product is delivered to the user base salary. When the development of this product mature enough to release to the end user, we entered the delivery phase.
Key delivery phase is to ensure that the software is available to end-users. Delivery stage can span several iterations, including preparing for the release of product testing, small tweaks based on user feedback.
Software product is delivered to the user after a period of time, if the new demand to start another development cycle, we start the next one , "initial, refinement, build and deliver" cycles. .
2, the software sort of disaster from start to finish
Twenty software disaster
1. Mariner ( Mariner ) fatal BUG (1962)
2. Hartford stadium collapse event (1978)
3. CIA to send natural gas to the Soviet Union (1982)
4. almost triggered World War III (1983)
5. Medical devices death case (1985)
6. Wall Street crash (1987)
7. AT & T phone off the network (1990)
8. Patriots live up to the soldier (1991)
9. long division defects Pentium (1993)
10. Ariane rocket explosion (1996)
11. Skynet bring Armageddon (1997)
12. Mars climate Orbiter crashed (1998)
13. disaster Research (1999)
14. British passport missing (1999)
15 years of the War Y2K (1999)
16. The Bomb (Dot-Bomb) crash (2000)
17. Love Bug (2000)
18 for the treatment of cancer death (2000)
19. The EDS abandoned its support for the child ( 2004)
20. the the FBI trilogy end (2005 )