📚 Program Development Life Cycle Stages Explained | 程序开发生命周期的各阶段详解
In computer science, the program development life cycle (PDLC) is a structured process used to plan, design, build, test, implement, document and maintain software. It gives developers a logical framework for managing complexity and reducing errors. For CIE students, the PDLC is an important syllabus topic because it explains how a program moves from an initial idea to a finished system and how it stays useful over time.
在计算机科学中，程序开发生命周期（PDLC）是一个用于规划、设计、构建、测试、实现、文档化和维护软件的结构化过程。它为开发者提供了一个逻辑框架，用以管理复杂性和减少错误。对于 CIE 学生而言，PDLC 是重要考点，因为它解释了程序如何从最初的想法演变为完整系统，以及如何长期保持可用。
1. Overview of the Program Development Life Cycle | 程序开发生命周期概述
The PDLC typically consists of a series of stages: requirements analysis, feasibility study, program design, coding, testing, implementation, documentation, maintenance and evaluation. Different textbooks may order these stages slightly differently. Some place implementation before full testing, while others use an iterative model where stages are repeated as the software is refined.
程序开发生命周期通常由一系列阶段组成：需求分析、可行性研究、程序设计、编码、测试、实现、文档化、维护和评估。不同教材对这些阶段的顺序略有不同。有些教材把实现放在完整测试之前；还有一些采用迭代模型，随着软件不断改进而重复各个阶段。
Regardless of the exact order, the most important idea is that each stage has a clear purpose and produces a specific output. If one stage is skipped, later stages become more difficult. For example, poor analysis leads to incorrect requirements, which then produce a program that does not match the user’s needs.
无论具体顺序如何，最重要的理念是每个阶段都有明确的目标并产生特定输出。如果跳过了某个阶段，后续阶段就会变得更加困难。例如，分析不充分会导致需求不正确，从而产生不符合用户需求的程序。
2. Analysis | 分析阶段
Analysis is the first major stage in most development projects. The analyst works with stakeholders, such as clients and end users, to understand exactly what the new program must do. This includes identifying the input data required, the output expected, the processing steps that must happen, and the data that needs to be stored permanently.
分析是大多数开发项目中的第一个主要阶段。系统分析员与利益相关者（如客户和最终用户）合作，准确理解新程序必须完成什么任务。这包括确定所需的输入数据、期望的输出结果、必须进行的处理步骤，以及需要永久存储的数据。
To gather requirements, the analyst may use several fact-finding methods. Interviews with users provide detailed opinions, questionnaires collect information from many people, observation shows how the current system works, and examination of existing documents reveals data flows and business rules.
为了收集需求，分析员可能会使用多种事实调查方法。与用户访谈可获得详细意见；问卷可以从许多人那里收集信息；观察能展示当前系统的工作方式；检查现有文档则可以揭示数据流和业务规则。
The key output of analysis is a requirements specification. This document often includes data flow diagrams, entity-relationship diagrams and a detailed list of functional and non-functional requirements. A clear requirements specification is essential because it is the foundation for all later design and coding work.
分析阶段的关键输出是需求规格说明书。该文档通常包含数据流图、实体联系图，以及详细的功能性需求和非功能性需求列表。清晰的需求规格说明至关重要，因为它是后续所有设计和编码工作的基础。
3. Feasibility Study | 可行性研究
Once the basic requirements are understood, the project team must decide whether it is worth developing the program. This is called a feasibility study. It usually considers technical feasibility, economic feasibility, legal feasibility and social or operational feasibility.
一旦理解了基本需求，项目团队必须判断开发该程序是否值得。这被称为可行性研究。它通常考虑技术可行性、经济可行性、法律可行性，以及社会或操作可行性。
Technical feasibility asks whether the existing hardware, software and programmer skills are sufficient to build the program. Economic feasibility compares the expected cost of development with the benefits it will bring. Legal feasibility checks whether the project complies with data protection and copyright laws. Social feasibility asks whether users are willing to accept the new system.
技术可行性询问现有硬件、软件和程序员技能是否足以构建该程序。经济可行性将预期开发成本与其带来的收益进行比较。法律可行性检查项目是否符合数据保护和版权法律。社会可行性则询问用户是否愿意接受新系统。
The output of this stage is a feasibility report. If the project is judged not feasible, it may be abandoned or redesigned. If it is feasible, the project moves on to the design stage.
该阶段的输出是可行性报告。如果项目被判断为不可行，则可能被放弃或重新设计。如果可行，项目将进入设计阶段。
4. Design | 设计阶段
During design, the requirements are converted into a technical solution that programmers can follow. The system is broken down into modules, data structures are planned, and algorithms are produced for each module. Good design makes the system modular, which means each component can be developed and tested independently.
在设计阶段，需求被转换为程序员可以遵循的技术解决方案。系统被分解为模块，数据结构得到规划，并为每个模块生成算法。良好的设计使系统模块化，这意味着每个组件都可以独立开发和测试。
Several design tools are used in this stage. Structure diagrams show the hierarchy of modules, pseudocode expresses algorithms in a language-independent way, flowcharts display the flow of control, and data dictionaries define every data item used by the system.
该阶段使用多种设计工具。结构图显示模块的层次关系，伪代码以与语言无关的方式表达算法，流程图展示控制流，数据字典定义系统中使用的每个数据项。
The design stage also decides the user interface. Input screens, output reports and error messages must be planned so that the program is user-friendly. At the end of this stage, a detailed program design document is produced.
设计阶段还要决定用户界面。必须规划输入屏幕、输出报告和错误消息，使程序对用户友好。该阶段结束时，会生成详细的程序设计文档。
5. Coding | 编码阶段
Coding, also called implementation of the code, is the stage in which the design is translated into source code using a programming language. The choice of language depends on the requirements, the target platform and the skills of the development team.
编码，也称为代码实现，是将设计转换为使用某种编程语言书写的源代码的阶段。语言的选择取决于需求、目标平台和开发团队的技能。
Good coding style is important. Programmers should use meaningful identifier names, consistent indentation, and appropriate comments. Modular programming, using functions and procedures, makes the code easier to read, test and maintain.
良好的编码风格非常重要。程序员应使用有意义的标识符名称、一致的缩进和适当的注释。使用函数和过程进行模块化编程，使代码更容易阅读、测试和维护。
During coding, programmers often perform small tests on the code they have just written. This is called unit testing, and it helps catch errors before the software is integrated into a complete system.
在编码期间，程序员通常会对自己刚编写的代码进行小型测试。这被称为单元测试，它有助于在软件集成到完整系统之前发现错误。
6. Testing | 测试阶段
Testing is the process of executing a program with the intention of finding errors. It is a controlled activity involving carefully selected test data. Testing aims to prove that the program meets its requirements and to identify situations in which it behaves incorrectly.
测试是以发现错误为目的来执行程序的过程。这是一种涉及精心选择测试数据的受控活动。测试旨在证明程序满足其需求，并识别程序行为不正确的情况。
Testing can be carried out at different levels. Unit testing checks individual modules; integration testing checks whether modules work together correctly; system testing checks the whole program; and acceptance testing verifies that the finished product meets the user’s requirements.
测试可以在不同级别上执行。单元测试检查单个模块；集成测试检查模块之间是否协调工作；系统测试检查整个程序；验收测试验证成品是否满足用户需求。
For every test level, test data must include normal data, boundary data and erroneous data. Normal data is valid input, boundary data is at the edge of the valid range, and erroneous data is deliberately invalid input that the program should reject gracefully.
对于每个测试级别，测试数据都必须包括正常数据、边界数据和错误数据。正常数据是有效输入；边界数据处于有效范围的边缘；错误数据则是故意设置的无效输入，程序应当妥善拒绝。
| Testing level | What is tested | Example |
| Unit testing | Individual function or procedure | Check that a calculation function returns the correct result |
| Integration testing | Combined modules | Check that the calculation module works with the input module |
| System testing | Whole system | Check the full program from input to output |
| Acceptance testing | Suitability for the client | Users test the program and accept or reject it |
Black-box testing uses only the specification to design test cases, without looking at the internal code. White-box testing examines the internal logic and ensures every path has been tested. Alpha testing is performed by developers and internal testers, while beta testing is performed by a small group of real users in a live environment.
黑盒测试只根据规格说明书设计测试用例，不查看内部代码。白盒测试检查内部逻辑，确保每条路径都经过测试。α测试由开发人员和内部测试人员执行，β测试则由一小群真实用户在真实环境中执行。
7. Implementation / Deployment | 部署（系统实施）阶段
After the program has passed testing, it is installed and brought into use. This stage is called implementation or deployment. Deciding how to switch from the old system to the new system requires careful planning, because errors during changeover can disrupt the organisation.
程序通过测试后，将被安装并投入使用。这一阶段称为实现或部署。如何从旧系统切换到新系统需要仔细规划，因为切换过程中的错误可能会干扰组织的正常运作。
Four common changeover methods are used. Direct changeover means the old system is stopped and the new system is started immediately. Parallel running means both systems operate at the same time for a period. Phased conversion introduces the new system in stages, and pilot running starts the new system in one part of the organisation before going live everywhere.
有四种常见的切换方法。直接切换是指旧系统停止，新系统立即启动。并行运行意味着两个系统同时运行一段时间。分阶段转换分步引入新系统，而试点运行则先在组织的一部分启动新系统，然后才全面推广。
| Method | Advantage | Disadvantage |
| Direct changeover | Immediate result; no extra cost | High risk if the new system fails |
| Parallel running | Old system can back up the new one | Extra cost; twice the data entry |
| Phased conversion | Low risk; easier to manage | Longer time to complete changeover |
| Pilot running | Tests suitability before full use | Only some users are involved at first |
The choice of changeover strategy depends on the size of the system, the cost of failure and the amount of training users need. After implementation, user training is often provided so that staff can operate the new program correctly.
切换策略的选择取决于系统规模、失败成本以及用户所需的培训量。实现后，通常会提供用户培训，以便员工能够正确操作新程序。
8. Documentation | 文档化阶段
Documentation is not a sudden final activity; it should be produced throughout the development cycle. There are two main types of documentation: user documentation and technical documentation. Both are essential for the long-term success of a program.
文档化并不是在最后突然进行的活动；它应在整个开发周期中持续产生。文档主要有两类：用户文档和技术文档。两者对程序的长期成功都很重要。
User documentation explains how to use the software. It includes installation instructions, an operating guide, a tutorial and descriptions of error messages. This helps ordinary users understand what to do and how to recover from mistakes.
用户文档解释如何使用软件。它包括安装说明、操作指南、教程和错误消息说明。这可以帮助普通用户了解应该做什么，以及如何从错误中恢复。
Technical documentation is written for programmers and system maintainers. It includes source code listings, design diagrams, algorithm explanations, data dictionary details and record of test runs. Good technical documentation makes maintenance much easier, especially when the original developers are no longer available.
技术文档是为程序员和系统维护人员编写的。它包括源代码列表、设计图、算法解释、数据字典细节和测试运行记录。好的技术文档使维护工作容易得多，尤其是当原始开发人员不再可用时。
9. Maintenance | 维护阶段
Once the program is in use, it will almost certainly need changes. Maintenance is the ongoing process of updating the software to fix faults, adapt to new environments, improve performance and prevent future problems. In many organisations, maintenance consumes the largest share of the total software budget.
程序投入使用后，几乎必然需要更改。维护是持续更新软件以修复故障、适应新环境、改进性能和预防未来问题的过程。在许多组织中，维护占据了总软件预算的最大份额。
There are four types of maintenance. Corrective maintenance fixes errors that were not discovered during testing. Adaptive maintenance adjusts the software to changes in the operating system or hardware. Perfective maintenance adds new features or improves performance. Preventive maintenance makes internal changes that make future maintenance easier.
维护有四种类型。修正性维护修复测试期间未发现的错误；适应性维护调整软件以适应操作系统或硬件的变化；完善性维护添加新功能或改进性能；预防性维护进行内部修改，使未来的维护更容易。
Maintenance requires good documentation and a clear record of version history. Without these, it is very difficult for a new programmer to understand why certain decisions were made and which parts of the system are more likely to need attention.
维护需要良好的文档和清晰的版本历史记录。如果没有这些，新程序员很难理解为什么做出某些决定，也很难判断系统的哪些部分更可能需要修改。
10. Evaluation | 评估阶段
Evaluation is the process of reviewing the finished and running system to see whether it achieves the original objectives. The evaluation may focus on correctness, efficiency, reliability, maintainability and usability. Input from users and performance data both play a role.
评估是审查已完成并正在运行的系统，判断其是否达到原始目标的过程。评估可能关注正确性、效率、可靠性、可维护性和易用性。用户反馈和性能数据都在评估中发挥作用。
If evaluation reveals problems, the project team returns to earlier stages. For example, new user requirements may arise, leading to a fresh analysis and design. This is why the program development life cycle is often shown as a circle rather than a straight line.
如果评估发现问题，项目团队将返回到较早的阶段。例如，可能会出现新的用户需求，导致重新分析和设计。这就是为什么程序开发生命周期往往被画成圆形而不是直线。
Modern agile methods take this idea further by repeating analysis, design, coding and testing in small cycles. Each cycle produces a usable part of the program, giving users something real to evaluate. However, even in agile methods, the same fundamental stages exist and must be managed carefully.
现代敏捷方法进一步延伸了这一理念，在小周期内重复分析、设计、编码和测试。每个周期都会产生一个可用的程序部分，给用户提供可以实际评估的东西。然而，即使在敏捷方法中，这些基本阶段仍然存在，并且需要谨慎管理。
Published by TutorHao | Computer Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导