Lifecycle Stages (Cambridge (CIE) A Level Computer Science): Revision Note

Lifecycle stages

What is the program development life cyle?

• The program development life cycle (PDLC) is a structured process used to design, build, and test software solutions

• It ensures that programs are developed systematically, efficiently, and to a high standard

• Each stage of the cycle has a specific purpose, and together they help developers solve real-world problems with reliable software

Analysis

• The analysis stage is all about understanding the problem the program is being created to solve

• Developers use abstraction to ignore unnecessary detail and focus only on what matters:

  • What the program must do (core functionality)

  • What limitations it must work within (constraints)

• The London Underground map is a great example of abstraction, you don’t need the real geography, just a clear route from stop A to stop B

• At this stage, a requirements document is often created. It:

  • Breaks the problem into manageable parts

  • Labels each requirement

  • Describes what success looks like for each feature

Design

• The design stage involves planning how the program will work

• Developers create a blueprint for the solution using tools such as:

  • Structure diagrams – break down the program into smaller components

  • Flowcharts – show the logical flow of processes

  • Pseudocode – outlines how the logic will be written in code

Coding

• In the coding stage, developers begin writing the program using a suitable programming language

• Code is written in modules that work together to solve the full problem

• Iterative testing is used – each module is tested and debugged individually as it’s created

• Modules are retested whenever changes are made, to ensure no new errors are introduced

Testing

• Once the full program is written, it is thoroughly tested using a variety of test data to ensure:

  • It meets all the original requirements

  • It handles valid and invalid input correctly

  • It performs reliably under different conditions

• Example test data: Alphanumeric sequences used to check password input validation

Maintenance

• After the program has been delivered to the client or end users, it enters the maintenance stage

• This involves:

  • Fixing bugs that weren't discovered during testing

  • Updating features to meet new requirements

  • Improving performance or adapting to new systems

• There are three main types of maintenance:

  • Corrective – fixing errors

  • Adaptive – updating the software to run on new hardware or platforms

  • Perfective – improving features based on user feedback

• Software maintenance ensures the program remains useful and reliable over time