System Design�

Design Objectives: System design is to deliver the requirements as specified in the feasibility report. The main objectives of the design are

1.���� Practicality

2.���� Efficiency

3.���� Cost

4.���� Flexibility

5.���� Security

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System design contains Logical Design & Physical Designing, logical designing describes the structure & characteristics or features, like output, input, files, database & procedures. The physical design, which follows the logical design, actual software & a working system. There will be constraints like Hardware, Software, Cost, Time & Interfaces.

The processing techniques are

������ Batch Processing

������ Real-time

������ Online

������ Combination of all

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Structured design is a data flow methodology. The graphical representation of data flow, communication� & defining the modules & their relationship with each is known as Structure Chart. This method decomposes & modularizes the system so that the complexity & manageability will come down. Thus reducing the intuitive reasoning & promotes the maintainable provable systems.

����������� This type of design follows top-down & hierarchy, which will have one single entry & single exit, The advantages of this method are

1.���� Critical interfaces are tested first

2.���� Early versions of the design, through incomplete are useful enough to resemble the real system

3.���� Structuring provides control & improve morale

4.���� The procedural characteristics define the order that determines processing.

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Major System Design Activities are

1.���� DB design

2.���� Program design

3.���� System & program test preparation

4.���� System Interface Specification

5.���� Audit Consideration

6.���� Audit control & Documentation control

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Major design process parts are

1.���� O/p design

2.���� I/p design

3.���� File Design

4.���� Procedure design

-�������� Computer design

-�������� Non-computer design

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5.���� Control design

These parts are inter-dependent on each other. System Specifications is a document, which will have a result of system design process, it serves as a Blue print for the project development & maintenance.

Prototype is a working system that is developed to test ideas & assumptions about a new system.

Objectives of Input Design are

1.���� Controlling amount of I/p

2.���� Avoiding delay

3.���� Avoiding errors in data

4.���� Avoiding extra steps

5.���� Keeping the process simple.

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Major concerns about the input

1.���� What input is needed

2.���� How & where is i/p is created

3.���� How should source documents designed

4.���� What format should be used for Input

5.���� What medium should be used to store data

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Input Verification can be done using

�Concerns for designing a CRT i/p screen

1.���� Easy to use

2.���� Improved processing speed

3.���� Menu driven Approach

4.���� Highlighting the information on screen

5.���� Usage of appropriate colors

6.���� Editing thru display screens

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Types of Outputs are

1.���� Application o/p

2.���� Operating O/p

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Output devices are

1.���� VDU

2.���� Printer

3.���� Computer output Microfilm (COM)

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Output Design Consideration are done using following points

Points to be considered while designing a Menu

1.���� Hierarchical

2.���� Termination

3.���� Skipping Menu

4.���� Security Control

Types of Forms

1.���� Action

2.���� Memory

3.���� Report

Computer Graphics are of three types:

1.���� Presentation graphics

2.���� Decision support Graphics

3.���� Graphics Hardware/software.

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Different types of files are

File organizations are

1.���� Sequential/Relational

2.���� Random

3.���� Indexed

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Major criteria for selecting a File organization are

1.���� Method of processing of file

2.���� Size of data

3.���� File inquiry capability�����������

4.���� File volatility

5.���� Response time

6.���� Activity ratio

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A database is a set of logically related files organized to facilitate access by one or more applications programs & to minimize data redundancy.
Main objectives of DB are:

1.���� Eliminate the redundancy of data

2.���� Data integrity

3.���� Share data among users

4.���� Incorporate changes quickly & easily

5.���� Simplify the use of data

6.���� Cost effective

7.���� Improve accuracy & consistency

8.���� Exercise central control over standards

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To manipulate the operations on the DB, a set of programs are maintained called Data Base management System (DBMS).
The Main advantages of DB are :

1.���� File consolidation

2.���� Program & file independence

3.���� Access versatility

4.���� Data Security

5.���� Program development

6.���� Program maintenance

7.���� Special information