System Analysis and Design Flashcards

Introduction to System Analysis and Design

Systems are created to solve problems, employing an organized approach.

Objectives

• Define a system.
• Explain the phases of the system development life cycle (SDLC).
• Enumerate the components of system analysis.
• Explain the components of system designing.

Defining a System

A system is a collection of components working together to achieve objectives.

• Basic system components:
  • Input
  • Processing
  • Output
• Components are interconnected and interdependent.
• Examples:
  • Human body (natural system)
  • Political system
  • Economic system
  • Educational system
• A well-designed system includes 'control' for feedback to achieve desired objectives.

System Life Cycle

An organizational process for developing and maintaining systems. It provides a list of processes and sub-processes for system development. SDLC is a combination of activities, also referred to as software development life cycle.

• Phases of System Development Life Cycle:
  • Preliminary study
  • Feasibility study
  • Detailed system study
  • System analysis
  • System design
  • Coding
  • Testing
  • Implementation
  • Maintenance

Phases of System Development Life Cycle

Preliminary System Study

• Initial stage, brief investigation of the system.
• Involves preparing a 'System Proposal' including:
  • Problem Definition
  • Objectives of the Study
  • Terms of reference for Study
  • Constraints
  • Expected benefits of the new system
• Prepared by System Analyst, presented to user management.
• Management may:
  • Accept the proposal
  • Reject the proposal
  • Request modifications
• Steps:
  • Problem identification and project initiation
  • Background analysis
  • Inference or findings (system proposal)

Feasibility Study

• Examines the system's feasibility regarding:
  • Workability
  • Meeting user's requirements
  • Effective use of resources
  • Cost-effectiveness.
• Categorized as:
  • Technical feasibility
  • Operational feasibility
  • Economic feasibility
  • Schedule feasibility
• Goal: To achieve the scope, not necessarily solve the problem.
• Estimates cost and benefits for Return on Investment (ROI).
• Defines resources needed for detailed investigation.
• Result: Feasibility report submitted to management.

Detailed System Study

• Detailed investigation based on the proposed system's objectives.
• Involves studying operations and their relationships within and outside the system.
• Data collection on available files, decision points, and transactions.
• Tools: Interviews, on-site observation, and questionnaires.
• Steps to define the new system:
  • Considering problems and new requirements
  • Workout the pros and cons including new areas of the system
• Documentation: Data flow diagrams (DFDs), data dictionary, logical data structures, and miniature specification.
• Main points:
  • Specification of the new system's goals based on user requirements.
  • Functional hierarchy showing functions and their relationships.
  • Functional network highlighting common functions.
  • List of attributes of the entities (data items).

System Analysis

• Process of collecting data, understanding processes, identifying problems, and recommending improvements.
• Involves studying business processes, gathering operational data, understanding information flow, finding bottlenecks, and evolving solutions.
• Includes subdividing complex processes, identifying data stores and manual processes.
• Objectives:
  • What is being done
  • How is it being done
  • Who is doing it
  • When is he doing it
  • Why is it being done
  • How can it be improved
• Thinking process, requires creative skills.
• Aims to create an efficient system that meets current needs and allows for future growth.
• Result: A logical system design.
• Iterative process until an acceptable solution emerges.

System Design

• Based on user requirements and detailed system analysis.
• Converts logical system design into physical system design.
• Stages:
  • Preliminary or General Design
    • Specifies features of the new system.
    • Estimates implementation costs and benefits.
  • Structured or Detailed Design
    • Computer-oriented work begins.
    • Detailed design of inputs, outputs, databases, forms, coding schemes, and processing specifications.
    • Selection of programming language, hardware, and software platform.
• Tools and techniques:
  • Flowchart
  • Data flow diagram (DFD)
  • Data dictionary
  • Structured English
  • Decision table
  • Decision tree
• System design involves:
  • Defining required system output
  • Determining data requirements
  • Determining medium and format of files and databases
  • Devising processing methods and software use
  • Determining data capture and input methods
  • Designing Input forms
  • Designing Codification Schemes
  • Detailed manual procedures
  • Documenting the Design

Coding

• Implementation of system design using a programming language.
• Conversion of program specifications into computer instructions.
• Programs coordinate data movements and control the entire process.
• Programs should be modular for fast development, maintenance, and future changes.

Testing

• Test run to remove bugs before implementation.
• Develop a test plan and run on test data; output should match expected results.
• System testing may be part of implementation.
• Test runs:
  • Program test
    • Individual testing of programs with prepared test data.
    • Debugging (error corrections).
  • System test
    • Testing the complete system with actual data.
    • Analyzing results and fixing errors.
    • User testing with their own data to ensure requirements are met.

Implementation

• Putting the developed system into practice after user acceptance.
• Steps:
  • Acquisition and Installation of Hardware and Software
  • Conversion
  • User Training
  • Documentation
• Hardware and software must be operational.
• Conversion: Converting data from the old system to the new format and setting up the database with security and recovery procedures.
• User training: Covering execution, data entry, processing, and report generation.
• Changeover strategies:
  • Direct Changeover: Complete replacement of the old system (risky).
  • Parallel run: Running both computerized and manual systems simultaneously (less risky, more expensive).
    • Manual results are compared with the results of the computerized system.
    • The operational work is doubled.
    • Failure of the computerized system at the early stage does not affect the working of the organization, because the manual system continues to work, as it used to do.
  • Pilot run: Running the new system with data from previous periods (less expensive and risky).
• Documentation:
  • User or Operator Documentation: How to use the system, including error messages.
  • System Documentation: System design, programs, coding, flow, data dictionary, and process description.

Maintenance

• Necessary to eliminate errors and tune the system.
• Review the system to check:
  • knowing the full capabilities of the system
  • knowing the required changes or the additional requirements
  • studying the performance.
• Major changes may require a new project through all life cycle phases.

Key to Intext Questions

1. (A) True (b) False (c) True (d) False (e) False
2. (a) first (b) detailed (c) logical data structure (d) structure design (e) pilot (f) manual