---

The Systems Life Cycle: A Deep Dive for IGCSE ICT Students

The systems life cycle is a structured approach to developing new computer systems or modifying existing ones. It ensures a systematic process from identifying a need to evaluating the final solution.

1. Systems Analyst:

The systems analyst is the key person in the systems life cycle. They are responsible for:

• Understanding: Analyzing the existing system and identifying problems or areas for improvement.
• Gathering Requirements: Interviewing users, conducting surveys, and analyzing data to determine what the new system needs to do.
• Designing Solutions: Creating a detailed plan for the new system, including hardware, software, and processes.
• Overseeing Implementation: Managing the development and testing of the new system and ensuring it is successfully deployed.

2. Analysis Stage:

The analysis stage is where the current system is thoroughly examined to understand its strengths, weaknesses, and user needs.

• Analyzing the Current System:
  • Observation: Watching how users interact with the system to identify inefficiencies or bottlenecks.
  • Questionnaires: Gathering feedback from a large number of users to get a broad perspective.
  • Interviews: Having in-depth conversations with key stakeholders to understand their specific needs and concerns.
  • Examination of Existing Documents: Reviewing user manuals, reports, and other documentation to learn about the system’s design and functionality.
• Inputs, Outputs, and Processing:
  • Inputs: The data that is entered into the system.
  • Outputs: The information that the system produces.
  • Processing: The steps the system takes to transform the inputs into outputs.
  • Data Flow Diagrams: Visual representations of how data moves through the system.
• User and Information Requirements:
  • Clearly defining what the users need from the new system and what information it should provide.
  • Requirements Specifications: A detailed document that outlines all the functional and non-functional requirements of the new system.
• Hardware and Software Identification and Justification:
  • Hardware:
    • Barcode Readers: For scanning product codes.
    • Scanners: For digitizing documents.
    • Touch Screens: For intuitive user interaction.
    • 3D Printers: For prototyping or creating physical models.
    • Large Monitors: For displaying complex data or graphics.
    • Speakers: For audio output.
  • Software:
    • Operating System: The foundation software on which other applications run.
    • Application Software: Programs that perform specific tasks, such as word processing or accounting.
  • Storage: Determining the size and type of storage needed to store data.

3. Design Stage:

This stage focuses on creating a blueprint for the new system.

• File Structure and Data Structures:
  • Deciding how data will be organized and stored, including the use of databases.
• Data Types:
  • Alphanumeric: Combination of letters, numbers, and symbols.
  • Characters: Individual letters, numbers, or symbols.
  • Text: Strings of characters.
• Validation Routines:
  • Range Check: Ensures data falls within a specified range.
  • Length Check: Ensures data has the correct number of characters.
  • Format Check: Ensures data is in the correct format (e.g., date, email address).
  • Presence Check: Ensures data is entered in a required field.
  • Check Digit: Calculates a digit based on other digits in a number to detect errors.
• Data Capture Forms:
  • Designing forms for users to input data, either on paper or electronically.
• Input Formats:
  • Determining how data will be entered into the system (e.g., keyboard, scanner).
• Output Formats, Screen Layouts, and Report Layouts:
  • Designing how information will be presented to the user, including screens, reports, and other visual elements.

4. Development and Testing Stage:

• Testing: Crucial to ensure the system works as intended and meets user requirements.
• Test Design:
  • Modular Development: Breaking the software into smaller modules that are easier to test individually.
• Test Strategies:
  • Black Box Testing: Testing the system’s functionality without knowledge of its internal workings.
  • White Box Testing: Testing the system’s internal structure and logic.
• Test Plans, Test Data, and Live Data:
  • Test Plan: A document outlining the specific tests to be performed.
  • Test Data: Data specifically created to test the system.
  • Live Data: Real data from the current system, used to test how the new system handles real-world scenarios.
  • Types of Test Data:
    • Normal Data: Data that falls within expected ranges.
    • Extreme Data: Data at the boundaries of acceptable ranges.
    • Abnormal Data: Data that should be rejected by the system.

5. Implementation Stage:

• System Implementation: The process of introducing the new system into the operational environment.
• Implementation Methods:
  • Direct Implementation: The old system is immediately replaced by the new system.
  • Parallel Implementation: Both systems run concurrently for a time, allowing for comparison and a smooth transition.
  • Pilot Implementation: The new system is introduced to a small group of users first to test it in a real-world setting.
  • Phased Implementation: The new system is introduced in stages or modules.

6. Documentation Stage:

• Technical Documentation: Detailed information about the system’s design, code, and technical specifications, meant for developers and IT professionals.
• User Documentation: Guides and manuals that explain how to use the system, meant for end-users.

7. Evaluation Stage:

• Evaluating a Solution: Assessing whether the new system meets the original objectives and user requirements. This involves gathering feedback from users, measuring system performance, and comparing the new system to the old one.