System Design System Design - Mr. Ahmad Al-Ghoul System Analysis and Design

System DesignSystem Design

- Mr. Ahmad Al-Ghoul- Mr. Ahmad Al-Ghoul

System Analysis and System Analysis and DesignDesign

AvicennaAvicennaSystem Analysis and Design System Analysis and Design

System Design System Design 22

learning Objectivelearning Objective

Explain the importance of Explain the importance of codes and describe various codes and describe various coding schemescoding schemes



Using Codes During System Using Codes During System DesignDesign

Overview of Overview of Codes A code is a set of letters or numbers that A code is a set of letters or numbers that

represents a data item. Codes can be used to represents a data item. Codes can be used to simplify output, input, and data formats. simplify output, input, and data formats.

Because codes often are used to represent data, you Because codes often are used to represent data, you encounter them constantly in your everyday lifeencounter them constantly in your everyday life

They save storage space and costs, reduce They save storage space and costs, reduce transmission time, and decrease data entry timetransmission time, and decrease data entry time

Can reduce data input errors in situations when the Can reduce data input errors in situations when the coded data is easier to remember and enter than the coded data is easier to remember and enter than the original source dataoriginal source data



Using Codes During System Using Codes During System DesignDesign Code exampleCode example

A ZIP code contains multiple items of information compressed into A ZIP code contains multiple items of information compressed into nine digitsnine digits

First digit identifies one of ten geographical areas of the USAFirst digit identifies one of ten geographical areas of the USA The next three digits identifies a major city or major distribution pointThe next three digits identifies a major city or major distribution point Fifth digit identifies an individual post office, an area within a cityFifth digit identifies an individual post office, an area within a city The last four digits identify a post office box or a specific street The last four digits identify a post office box or a specific street

addressaddress

Broad geographical area in eastern U.S

Elizabeth City, NC

Local postal delivery point

Specific location for College of the Albemarle




Types of CodesTypes of Codes Companies use many different coding Companies use many different coding

methodsmethods Codes should be easy to learn and applyCodes should be easy to learn and apply When the analyst crate codes for the When the analyst crate codes for the

information system, he first should obtain information system, he first should obtain comments and feedback from userscomments and feedback from users

We will describes seven common coding We will describes seven common coding methodsmethods




Types of CodesTypes of Codes1. Sequence codes: Sequence codes are numbers : Sequence codes are numbers

or letters assigned in a specific order. Sequence or letters assigned in a specific order. Sequence codes contain no additional information other codes contain no additional information other than an indication of order of entry into a than an indication of order of entry into a system. system.

2. Block sequence codes: use blocks of numbers : use blocks of numbers for different classificationfor different classification

3. Alphabetic codes: use alphabet letters to : use alphabet letters to distinguish one item from another based on a distinguish one item from another based on a category, an abbreviation, or an easy-to-category, an abbreviation, or an easy-to-remember value, called a remember value, called a mnemonic mnemonic code. code. Many classification codes fit more than one of Many classification codes fit more than one of the following definitions:the following definitions:




Types of CodesTypes of Codesa.a. Category codes: identify a group of related items. For Category codes: identify a group of related items. For

example, a local department store may use a two-example, a local department store may use a two-character category code to identify the department character category code to identify the department in which a product is sold. in which a product is sold.

b.b. Abbreviation codes: Abbreviation codes are Abbreviation codes: Abbreviation codes are alphabetic abbreviations. For example, standard alphabetic abbreviations. For example, standard state codes include NY for New York, ME for Maine, state codes include NY for New York, ME for Maine, and MN for Minnesota. – mnemonic codes: use a and MN for Minnesota. – mnemonic codes: use a specific combination of letters that are easy to specific combination of letters that are easy to remember. Many three-character airport codes are remember. Many three-character airport codes are mnemonic codes. For example, LAX represents Los mnemonic codes. For example, LAX represents Los Angeles International Airport Angeles International Airport




Types of codesTypes of codes4.4. Significant digit codes: Significant digit codes Significant digit codes: Significant digit codes

distinguish items by using a series of distinguish items by using a series of subgroups of digits. ZIP codes, for example, subgroups of digits. ZIP codes, for example, are significant digit codes. are significant digit codes.

Aisle number

Floor number

Section code Bin numberWarehouse location code

Sample of a code that uses significant digits to pinpoint the location of an inventory item.




Types of codesTypes of codes5.5. Derivation codes: Derivation codes Derivation codes: Derivation codes

combine data from different item combine data from different item attributes, or characteristics, to build attributes, or characteristics, to build the code. Most magazine subscription the code. Most magazine subscription codes are derivation codes. codes are derivation codes.

A magazine subscriber code is derived from various parts of the name and address.




Types of codesTypes of codes6.6. Cipher codes: Cipher codes use a keyword to Cipher codes: Cipher codes use a keyword to

encode a number. A retail store, for example, encode a number. A retail store, for example, may use a 10-letter word, such as may use a 10-letter word, such as CAMPGROUND, to code wholesale prices, CAMPGROUND, to code wholesale prices, where the letter C represents 1, A represents where the letter C represents 1, A represents 2, and so on. 2, and so on.

7.7. Action codes: Action codes indicate what Action codes: Action codes indicate what action is to be taken with an associated item. action is to be taken with an associated item. For example, a student records program might For example, a student records program might prompt a user to enter or click an action code prompt a user to enter or click an action code such as D (to display the student's record), A such as D (to display the student's record), A (to add a record), and X (to exit the program). (to add a record), and X (to exit the program).




Developing a CodeDeveloping a Code Codes should be easy to remember, decipher, Codes should be easy to remember, decipher,

and verifyand verify Keep the following suggestions in mind when Keep the following suggestions in mind when

developing a code:developing a code:1.1. Keep codes concise. Do not create codes that are Keep codes concise. Do not create codes that are

longer than necessarylonger than necessary

2.2. Allow for expansion. A coding scheme must allow for Allow for expansion. A coding scheme must allow for reasonable growth in the number of assigned codesreasonable growth in the number of assigned codes

3.3. Keep codes stable. Changes in codes can cause Keep codes stable. Changes in codes can cause consistency problems and require data updates. consistency problems and require data updates. During the changeover period, you have to change During the changeover period, you have to change all the stored occurrence of a particular code and all all the stored occurrence of a particular code and all documents containing the old code, as users switch documents containing the old code, as users switch to the new codeto the new code




Developing a CodeDeveloping a Code4.4. Make codes unique. Codes used for Make codes unique. Codes used for

identification purposes must be unique to identification purposes must be unique to have meaninghave meaning

5.5. Use sortable codes. ensures that data sorts Use sortable codes. ensures that data sorts into usable groups. into usable groups.

6.6. Avoid confusing codes. Avoid allowing both Avoid confusing codes. Avoid allowing both letters and numbers to occupy the same letters and numbers to occupy the same positions within code because some of those positions within code because some of those are easily confused, like the number 0 and the are easily confused, like the number 0 and the letter O letter O




Developing a CodeDeveloping a Code7.7. Make codes meaningful. Codes must be easy to Make codes meaningful. Codes must be easy to

remember, useful for users, remember, useful for users, convenientconvenient to use, to use, and easy to encode and interpret. Using ENG as and easy to encode and interpret. Using ENG as the code for the English department is easier to the code for the English department is easier to interpret and remember than either XVA or 132interpret and remember than either XVA or 132

8.8. Use a code for a single purpose. Do not use a Use a code for a single purpose. Do not use a single code to classify two or more unrelated single code to classify two or more unrelated attributes.attributes.

9.9. Keep codes consistent. For example, if the Keep codes consistent. For example, if the payroll system already is using two digit codes payroll system already is using two digit codes for departments, do not create a new, different for departments, do not create a new, different coding scheme for the personal systemcoding scheme for the personal system



Sequence SummarySequence Summary You learned that a code is a set of letters or You learned that a code is a set of letters or

numbers used to represent data in a systemnumbers used to represent data in a system By using codes, you can speed up data By using codes, you can speed up data

entry, reduce data storage space, and entry, reduce data storage space, and reduce transmission timereduce transmission time

Codes also can be used to reveal or to Codes also can be used to reveal or to conceal informationconceal information

The main types of codes are sequence The main types of codes are sequence codes, block sequence codes, classification codes, block sequence codes, classification codes, alphabetic codes (including category codes, alphabetic codes (including category codes, abbreviation codes, and mnemonic codes, abbreviation codes, and mnemonic codes), significant digit codes, derivation codes), significant digit codes, derivation codes, cipher codes, and action codescodes, cipher codes, and action codes



Sequence SummarySequence Summary

In this Sequence we haveIn this Sequence we have Defined the term codeDefined the term code Explained theExplained the the importance of codes the importance of codes described various coding schemes described various coding schemes

including sequence codes, block including sequence codes, block sequence codes, classification codes, sequence codes, classification codes, alphabetic codes (including category alphabetic codes (including category codes, abbreviation codes, and codes, abbreviation codes, and mnemonic codes), significant digit mnemonic codes), significant digit codes, derivation codes, cipher codes, codes, derivation codes, cipher codes, and action codesand action codes



ReferenceReference

[1] System Analysis and Design, Sixth [1] System Analysis and Design, Sixth EditionEdition

Authors: Gary B. Shelly, Thomas J. Authors: Gary B. Shelly, Thomas J. Cashman and Harry J. Rosenblatt Cashman and Harry J. Rosenblatt

Publisher: SHELLY CASHMAN Publisher: SHELLY CASHMAN SEWIES.SEWIES.

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System Design System Design - Mr. Ahmad Al-Ghoul System Analysis and Design