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1. Systems and Software

Development

1.1 The Systems Life Cycle

1.1.5 Design: Parts of a System

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The design phase

•Design - different possible solutions (hardware and software) get considered, prototyped and built.

•Design is also done in a modular way (splitting the problem down into its component parts).

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System flow charts

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System flow charts

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System flow charts

•Action or process

•Input or output device

•Data flow

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LaserLaserprinterprinter

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System flow charts

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Some questions to ask

•Should computers be used at all?

•Should standard software packages be used?

•How much customisation is desirable/allowed?

•Should the system be centralised or distributed?

•Stand-alone or networked?

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Some questions to ask

•Which data should/should not be held on the system?

•Where will the input data come from and how will it be entered?

‣Manual (mouse, keyboard, touch screen...)?

‣Direct (barcode reader, OMR, OCR, MICR...)?

‣Automatic (sensors, timers...)?

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Some questions to ask

•What kind of output should be produced?

‣Soft (storage, screen, speaker...)?

‣Hard (printer, plotter...)?

‣Actuator (electric, hydraulic, pneumatic...)?

•What is the best output layout (forms, reports, graphic design...)?

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Some questions to ask

• What is the best human-computer interface?

‣ Command line?

‣ Menu-driven?

‣ GUI?

• What are the best file formats?

‣ One (flat) file or many (relational) files?

‣ What type of access (single user, multi-user...)?

‣ dat, txt, doc, csv...?

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Some questions to ask

• What data structures are needed in the system?

‣ Arrays?

‣ Dynamic/static (HL)?

‣ Stacks/queues (HL)?

‣ Lists/trees (HL)?

• What hardware components should be adapted or purchased?

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Some questions to ask

• Questions about the nature of the information that will enter and leave the system are collectively called the data requirements.