Course: IKI81404T : Perancangan Sistem Informasi

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Pow erPoint Course Mat erial for SCELE Graduat e Program I nform at ion Technology

Facult y of Com put er Science – UNI VERSI TY OF I NDONESI A

PERANCANGAN SISTEM INFORMASI

Session 9 Program Design

Based on System Analysis & Design 2

nd

_Edition

Authors : Alan Dennis & Barbara Haley Wixom

Publisher : John Wiley & Sons

Session 9 Program Design

Based on System Analysis & Design 2

nd

_Edition

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Pow erPoint Course Mat er ial for SCELE Graduat e Program I nform at ion Technology Fa cu lt y of Com put e r Scie n ce – Unive r sit y of I n don e sia

Objectives

Be able to create a structure chart

Be able to write a program specification

Understand the use of pseudocode

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Key Definitions

Program design

- creating instructions for the

programmers

The

top-down, modular approach

- begin with

the “big picture” and gradually add detail

Program design document

– all structure

charts and specifications needed by

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The Structure Chart

Important program design technique

Shows all components of code in a hierarchical

format

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Building the Structure Chart

Processes in the DFD tend to represent one

module on the structure chart

Afferent processes – provide inputs to system

Central processes – perform critical system

operations

Efferent processes – handle system outputs

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Types of Structure Charts

Transaction

structure – control module calls

subordinate modules, each of which handles a

particular transaction

Many afferent processes

Few efferent processes

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Types of Structure Charts

Transform

structure – control module calls

several subordinate modules in sequence

Each subordinate performs a step in a process

that transforms an input into an output

Few afferent processes

Many efferent processes

Lower levels of structure chart

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Steps in Building the Structure Chart

1. Identify top level modules and decompose

them into lower levels

2. Add control connections

3. Add couples

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Design Guidelines

High quality structure charts result in

programs that are modular, reusable and easy

to implement.

Measures include:

Cohesion

Coupling

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Example of Low Cohesion

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Cohesion Decision Tree

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Factoring

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Your Turn

What, if anything, happens to coupling when

you create modules that are more cohesive?

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Fan-in

High fan-in preferred

Promotes reuse of subordinate modules

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Quality Checklist

1. Library modules have been created where ever possible

2. The diagram has a high fan-in structure

3. Control modules have no more than 7 subordinates

4. Each module performs only one function (high cohesion)

5. Modules sparingly share information (loose coupling)

6. Data couples that are passed are actually used by the

accepting module

7. Control couples are passed from “low to high”

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Program Specifications Content

No standard approach

Include program information

Note events that trigger actions

List inputs and outputs

Include pseudocode

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Pseudocode Example

( Get CD- info m odule)

Accept ( CD_t it le) { Required}

Accept ( CD_art ist ) { Required}

Accept ( CD_cat egory) { Required}

Accept ( CD_lengt h)

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CASE Tool View of Process Description

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