System Development Life Cycle
(vs. Prototyping)

Systems Development Life Cycle Benefits (some)

Benefits

• Improve quality of systems
• Reduce maintenance costs
• Increase user service

Systems Development Life Cycle STEPS

Requests

• Written by user
• information requirements defined
• users description of application
• New or modification of application
• State business need
• Reviewed by steering committee

Feasibility Study

• Benefits to be obtained
• Objective
• Detailed sufficiently
• Impact on user
• Budget
• Cost/benefits analysis
• Alternatives - ex: vendor software available
• Pay-back
• Compatibility with environment - software & hardware
• Additional MIS resources needed
• Analyze existing system
• Implementation schedule
• Approval/disapproval - user, MIS, steering committee

General Systems Design - high level

• Analyze existing system - inputs, processing, outputs
• Detail user requirements
• Specify what system is to accomplish
• Review alternatives
• vendor packages vs. built in-house
• main frame, LAN, microcomputer, etc.

Detailed Systems Design

• Approaches
• Top-down – general purpose to refined details
• Analyze co. goals & objectives, policies, procedures
• Determine decisions to be made & information needed by management
• Evaluate management information needs vs. efficient processing
• Structured/Modular
• Define each module/subsystem
• Minimizes interdependence
• Hierarchy-input-process-output (HIPO)
• Stylized charts depict detailed levels of systems
• Documentation technique by IBM
• Systems design & programming standards
• Program specifications
• Workflows & programming (no coding)
• File layouts
• Reports, screen layouts
• System flowcharting standards
• System narrative
• Database – modify or design
• Data conversion procedures
• Controls
• Transaction trails
• Uniform processing of transactions; like transactions processed same way
• Initiation/subsequent execution of transactions
• Automatically performed
• Management approved
• Hardware
• Security
• Data communications
• Test plans
• Quality assurance
• Data element definitions - each field in each file listed & defined, etc.
• Procedure manuals – technical, forms, etc.

Coding Programs

• Code programs from specifications determined in systems design phase
• Computer system changes
• Strict control
• Use working copy when redesigning program
• Structured programming
• Divide programs into modules by functions
• Code programs separately
• Facilitates security
• Speeds development
• Facilitates maintenance
• Computer aided systems engineering (CASE)
• Maintain all system documentation on computer
• Automate some of coding process

Testing programs

• Test each program
• Use incomplete/incorrect data
• Test all branches of program
• Test edit capabilities
• Compare with expected results
• User tests & accepts changes and test results
• System test - test series of programs in sequence

Converting

• Convert data files - from old to new system
• Control conversion - record counts, hash totals, reconciliation's, etc.
• Review & sign-off

Implementing

• Run parallel old & new system - if possible
• Convert by module
• Train and educate users

Maintenance

• Change controls
• Modifications/changes
• authorized
• compare code for unauthorized program changes
• per standards
• tested
• approved by user & MIS management
• Follow-up

Prototyping (vs. systems development life cycle)

• Develop and put into operation refined versions of systems
• Design later when necessary information available

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