System Design

Learning Objectives
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System Analysis and Design
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Introduction
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Input technology has changed dramatically in recent years
Modern systems use the new technology to speed up the input process, reduce costs, and capture data in new forms
The quality of the output is only as good as the quality of the input, known as Garbage in, garbage out (GIGO)
Systems developers know that the best time to avoid problems is when data entered
The main objective of input design is to ensure the quality, accuracy, and timeliness of input data
During input design, you determine how data will be captured and entered into the system
Data capture uses an automated or manually operated device to identify source data and convert it to computer-readable form.
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Input Design
 Input design main objectives
 Select a suitable input and data entry method
 Reduce input volume
 Design attractive data entry screens
 Use validation checks to reduce input errors
 Design required source documents
 Develop effective input controls
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Input Design
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Identify devices and mechanisms used to enter input
 High-level review of most up-to-date methods to enter data
Identify all system inputs and develop list of data content with each
 Provides link between design of application software and design of user and system interfaces
Determine controls and security necessary for each system input
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Input Devices and Mechanisms
 Capture data as close to origination source as possible
 Use electronic devices and automatic entry whenever possible
 Avoid human involvement as much as possible
 Seek information in electronic form to avoid data reentry
 Validate and correct information at entry point
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Prevalent Input Devices to Avoid Human Data Entry
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Input Design
 Input and Data Entry Methods
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Input process should be efficient, timely, and logical
System analysts should study system transactions and business operations to determine how and when data should enter the system
First thing to think about is whether to use batch or online input methods
 When determine whether to use batch or online input the analyst must consider the following factors
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Batch input data entry usually performed on specified time schedule such as daily, weekly, monthly, or longer
Online input offers many advantages, including the immediate validation and availability of data
 A popular online input method is Source data automation which combines online data entry and automated data capture using input devices such as magnetic data strips, or swipe scanners.
 Source data automation is fast and accurate, and minimize human involvement
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Input Design
 Input and Data Entry Methods
 Examples of source data automation are
 Automatic teller machines (ATMs) that read data strips on bank cards
 Factory employees who use magnetic ID cards to clock on and off specific jobs so the company can track production costs accurately
 Libraries that use handled scanners to read optical strips on books
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Input Design
 Input and Data Entry Methods
 Tradeoffs between batch input and online input
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The decision to use batch or online input depends on business requirements
Unless source data automation is used, manual data entry is slower and more expensive than batch input because it is performed at the time the transaction occurs and often done when computer demand is at its highest
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Input Design
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Input Volume
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To reduce input volume, you must reduce the number of data items required for each transaction
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When you reduce input volume, you avoid unnecessary labor costs, get the data into the system more quickly, and decrease the number of errors
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Guidelines will help reduce input volume
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Input necessary data only. Do not input the data item unless it is needed by the system.
Do not input data that the user can retrieve from system files or calculate from other data
Do not input constant data
Use codes. Codes are shorter than the data they represent, and coded input can reduce data entry time
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Input Design
 Designing Data Entry Screens
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Most effective method of online data entry is form filling, in which a blank form that duplicates or resembles the source document is completed on the screen
Guidelines to help design data entry screens
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Restrict user access to screen locations where data is entered design forms with proper flow, from left to right and top to bottom group information logically
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Provide a descriptive caption for every field, and show the user where to enter the data and the required or maximum field size
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Input Design
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Designing Data Entry Screens
Guidelines to help design data entry screens
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Display a sample format if a user must enter values in a field in a specific format
Require an ending keystroke for every field, by pressing the ENTER or the TAB key. Avoid a design that moves automatically to the next item when the field is full
Do not require users to type leading zeroes for numeric fields
Do not require users to type trailing zeroes for numbers that include decimals
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Input Design
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Designing Data Entry Screens
Guidelines to help design data entry screens
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Display default values so operators can press the
ENTER key to accept the suggested value
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Use a default value when a field value will be constant for successive records or throughout the data entry session
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Display a list of acceptable values for fields by providing a drop-down list box containing acceptable values that allows users to select a value by clicking, and provide meaningful error messages
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Input Design
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Designing Data Entry Screens
Guidelines to help design data entry screens
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Provide a way to leave the data entry screen at any time without entering the current record
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Provide users with an opportunity to confirm the accuracy of input data before entering it by displaying a message such as, add this record?
(y/N).
Provide a means for users to move among fields on the form
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Input Design
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Designing Data Entry Screens
Guidelines to help design data entry screens
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Design the screen form layout to match the layout of the source document
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Allow users to add, change, delete, and view records
Provide a method to allow users to search for specific information
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Input Design
Good Flow in a Form
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Bad Flow in a Form
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Sequence Summary
Input design has six main objectives: select a suitable input and data entry method, reduce input volume, design attractive data entry screens, use validation checks to reduce input errors, design required source document, and develop effective input controls
The system analyst must consider three key procedures: data capture, data entry, and input methods
Data capture involves identifying and recording source data
Data entry involves converting a source data into a computerreadable form and entering it into the system.
A wide variety of input media is available, including optical, voice, and magnetic recognition devices; special purpose terminals; and graphical input devices
An effective way to reduce input errors is to reduce input volume
There are many guidelines to design a data entry screens such as design forms with proper flow, provide a descriptive caption for every field, group information logically, require an ending keystroke for every field, do not require users to type leading or trailing zeroes, display default values, display a list of acceptable values for fields, allow users to add, change, delete, and view records, and provide a method to allow users to search for specific information
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Sequence Summary
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[1] System Analysis and Design, Sixth Edition
Authors: Gary B. Shelly, Thomas J. Cashman and Harry J. Rosenblatt
Publisher: SHELLY CASHMAN SEWIES.
[2] system analysis and design, sixth edition
Authors: Kenneth E. Kendall and Julie E.
Kendall
Publisher: Prentice Hall
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