1. Planning stage-11950s to11960s.

2. Program System Stage-1960s and 1970s

3. Software engineering stage-after 1970s.

software life cycle

Definition phase, development phase and maintenance phase.

Waterfall model

Planning, requirements analysis, design, coding, testing, operation and maintenance.

1. Make a plan

Determine the overall goal of developing software systems,

The functional performance, reliability and interface requirements are given.

Feasibility study of completing software tasks,

Estimate the cost-effective development progress of available resources,

Formulate the implementation plan for completing the development task and submit it to the management department for review together with the feasibility study report.

2. Requirements analysis and definition

Analyze the requirements put forward by users and give a detailed definition.

Compile the software requirement specification or system function specification and the preliminary system user manual,

Submitted to the management department for review,

3. Software design

master design

Detail design

4. programming; arrange

5. Software testing

Unit test, assembly test and effectiveness test.

6. Use and maintenance

Corrective maintenance, adaptive maintenance and perfect maintenance.