I'System Design is the process of developing specifications for a proposed new system from the recom

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Lecture 4

• Chapter 7

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I. System Design is the process of developing
specifications for a proposed new system from the
recommendations made during Systems Analysis.
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Benefits 1. allows the project team to identify
problems in the proposed system before
implementation 2. allows management the
opportunity to approve, revise, or disapprove the
system before implementation.
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II. Preliminary System Design a high level,
general description of the system that
includes A. Statement of Scope defines the
boundaries of the system
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B. System Requirements the features necessary for
the system to achieve its objectives 1. Outputs
Reports and Terminal Displays 2. Data Data
entities and their attributes 3. Processes
Procedures and Computer Programs 4. Inputs
Source Documents and Direct Data Entry 5.
Policies Established by top management
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C. Resource Requirements an estimate of the
financial, hardware, and software resources
needed to meet system requirements. 1. Software
sources affect financial resources In house
Development Software Development
Companies Computer Manufacturers User Groups
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2. Considerations in the Make or Buy Decision
(16 17) - User Acceptance - Required
Modifications - Installation Time - Quality of
Instruction Manuals - Installation Cost
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3. Hardware sources also affect the financial
resources required Purchase Lease or
rental Service Bureau Remote Batch Timesharing
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Detailed Specification Requirements
Definition -output specification -data
specification -input specification -computer
program spec. -others
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Equipment Selection Evaluation of Equipment
Vendors RFP Equipment Performance Adaptability
Vendor Support Vendor Availability Cost
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ILLUSTRATION 7-3 Considerations in the
Make-or-Buy Decisions for Software User
Acceptance In-house. Programs customized to
users' preferences. External package. Users adapt
to requirements of externally written
programs. Required Modifications In-house. No
modifications required. External package.
Modifications may be necessary to make software
acceptable. Installation Time In-house. Measured
in months or years. External package. Measured in
weeks or months. Quality of Instruction Manuals
In-house. Time pressures may discourage
preparation of good documentation. External
package. Documentation available for review prior
to purchase. Installation Cost In-house. Costly
all costs absorbed by one system. External
package. Less costly developmental costs
absorbed by many systems.
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Software Acquisition -Review the
requirements -Identify Available
packages -narrow the choice -perform detailed
comparison -talk to users -benchmark
test select a package
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A. Requirements Definition 1. Output
Specifications Display Screens Illustration
7-6 Report Layouts Illustration 7-7
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2. Data Specifications Record Layout Illustration
7-8
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3. Input Specifications Forms Design Illustration
7-9
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4. Program Specifications Program
Narrative Illustration 7-10 Structure Chart
Illustration 7-11 Pseudocode Illustration 7-12
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5. Manual Procedure Specifications Procedure
Descriptions Illustration 7-13
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B. Select Source for Hardware Criteria for
Equipment Evaluation 1. Equipment Performance
difficult to measure properly 2. Adaptability
includes expandability and compatibility 3.
Vendor Support quality of technical help 4.
Availability affects the Implementation
schedule 5. Cost tangible costs of installation
and operation
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ILLUSTRATION 7-16 Steps in Software
Acquisition 1. Review the requirements. Define
these requirements during detailed system
specification. 2. Identify available packages.
Identify packages being marketed for this
application. 3. Narrow the choices. Eliminate
those not satisfying system requirements. 4.
Perform a detailed comparison. Evaluate
thoroughly the features of each package. 5. Talk
to users. Interview people experienced with the
package. 6. Conduct benchmark tests. Execute the
package on the actual computer equipment. 7.
Select a package. Make a choice based on
features, interviews, and tests.
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D. Report to Management a description of the
recommended system, based on the documentation
created during design Executive
Summary Objective and Scope
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IV.Auditor Involvement in System Design A.
During the specifications review 1.
Reports adequacy of audit trail adequacy of
internal control 2. Processing steps use of
control procedures 3. Data files security
accuracy backup procedures retention
practices 4. Equipment Selection should be in
accordance with management's policies
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B. Create audit modules allow the use of the
computer in the audit