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IB Computer Science. Chapter 1. System Life Cycle And Software Development. System Life Cycle. Data Collection. Who inputs data to the system. What form the data is in. Any validation that is needed. Data collection techniques : Interviews Questionnaires Search existing documents

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Chapter 1

IB Computer Science

Chapter 1

System Life Cycle And

Software Development



Data collection
Data Collection

  • Who inputs data to the system.

  • What form the data is in.

  • Any validation that is needed.

  • Data collection techniques:

    • Interviews

    • Questionnaires

    • Search existing documents

    • Search literature for other solutions

    • Observe people working with the existing system.


Requirements specification
Requirements specification

  • List of hardware and software tools needed.

    • e.g.: RAM, HDD, CPU, GPU, Monitor, etc.

  • Description of functions of the hardware and software in the completed system.

  • List of personnel and the tasks which will be assigned to them.


Feasibility report
Feasibility Report

  • Estimated costs

  • Expected benefits

  • Completion time estimates

  • Potential difficulties


System testing
System Testing

  • Normal Data

    • within normal limits

  • Extreme Data

    • outside normal limits (e.g. out of bounds)

  • Abnormal Data

    • unexpected data (e.g. different data type)


Methods of implementing new systems
Methods of Implementing New Systems

  • Parallel running

  • Phased introduction

  • Direct changeover (“big bang”)

    • discuss pros and cons of each


Data capture and presentation
Data Capture and Presentation

  • Manual data entry

    • keyboard, mouse, touch screen

  • Direct data entry

    • OCR/OMR scanners, MICR reader, barcode scanner

  • Automatic data entry

    • Sensors (temperature, sound, pressure, light, etc)


Output methods
Output methods

  • Temporary display

    • Monitors, projectors, VDU (visual display units)

  • Permanent display

    • Printers, plotters

  • Electrical/mechanical output

    • Actuators (relays, switches, converters, etc)


User interfaces
User Interfaces

  • Command Line Interface

    • Easier to program

    • Requires less hardware resources

    • Users need to remember specific commands

    • Long term users may find it quicker to operate

  • Graphical User Interface

    • More complex to implement

    • Requires more hardware resources

    • Easier for users (especially the novice users)


System flowcharts
System flowcharts

Action or process

Input or Output

Online storage

Condition / branching

Disc storage



System documentation
System Documentation

  • Intended for programmers who have to understand the program to maintain it

  • Internal documentation:

    • Meaningful identifiers

    • Keeping methods small and classes concise

    • Comments

    • Indentations


System documentation cont
System Documentation (cont.)

  • External documentation

    • Purpose of the program

    • Data flow in the system

    • Hardware and software requirements (platform)

    • Structure of the program (module diagram)

    • Descriptions of all modules (methods)

      • purpose, interface, variables


User documentation
User Documentation

  • System/hardware requirements

  • How to install

  • How to run

  • Sample input/output

  • Troubleshooting

  • Help button (and/or online help)


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