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

Avicenna System Analysis and Design System Design2 learning Objective Explain the importance of codes and describe various coding schemes Explain the importance of codes and describe various coding schemes

Avicenna System Analysis and Design System Design3 Using Codes During System Design Overview of Codes Overview of CodesCodes A code is a set of letters or numbers that represents a data item. Codes can be used to simplify output, input, and data formats. A code is a set of letters or numbers that represents a data item. Codes can be used to simplify output, input, and data formats. Because codes often are used to represent data, you encounter them constantly in your everyday life Because codes often are used to represent data, you encounter them constantly in your everyday life They save storage space and costs, reduce transmission time, and decrease data entry time They save storage space and costs, reduce transmission time, and decrease data entry time Can reduce data input errors in situations when the coded data is easier to remember and enter than the original source data Can reduce data input errors in situations when the coded data is easier to remember and enter than the original source data

Avicenna System Analysis and Design System Design4 Using Codes During System Design Code example Code example A ZIP code contains multiple items of information compressed into nine digits A ZIP code contains multiple items of information compressed into nine digits First digit identifies one of ten geographical areas of the USA First digit identifies one of ten geographical areas of the USA The next three digits identifies a major city or major distribution point The next three digits identifies a major city or major distribution point Fifth digit identifies an individual post office, an area within a city Fifth digit identifies an individual post office, an area within a city The last four digits identify a post office box or a specific street address The last four digits identify a post office box or a specific street address Broad geographical area in eastern U.S Elizabeth City, NC Local postal delivery point Specific location for College of the Albemarle

Avicenna System Analysis and Design System Design5 Using Codes During System Design Types of Codes Types of Codes Companies use many different coding methods Companies use many different coding methods Codes should be easy to learn and apply Codes should be easy to learn and apply When the analyst crate codes for the information system, he first should obtain comments and feedback from users When the analyst crate codes for the information system, he first should obtain comments and feedback from users We will describes seven common coding methods We will describes seven common coding methods

Avicenna System Analysis and Design System Design6 Using Codes During System Design Types of Codes Types of Codes 1. Sequence codes: Sequence codes are numbers or letters assigned in a specific order. Sequence codes contain no additional information other than an indication of order of entry into a system. Sequence codes Sequence codes 2. Block sequence codes: use blocks of numbers for different classification Block sequence codes Block sequence codes 3. Alphabetic codes: use alphabet letters to distinguish one item from another based on a category, an abbreviation, or an easy-to-remember value, called a mnemonic code. Many classification codes fit more than one of the following definitions: Alphabetic codes Alphabetic codes

Avicenna System Analysis and Design System Design7 Using Codes During System Design Types of Codes Types of Codes a. Category codes: identify a group of related items. For example, a local department store may use a two- character category code to identify the department in which a product is sold. Category codes Category codes b. Abbreviation codes: Abbreviation codes are alphabetic abbreviations. For example, standard state codes include NY for New York, ME for Maine, and MN for Minnesota. – mnemonic codes: use a specific combination of letters that are easy to remember. Many three-character airport codes are mnemonic codes. For example, LAX represents Los Angeles International Airport Abbreviation codes mnemonic codes Abbreviation codes mnemonic codes

Avicenna System Analysis and Design System Design8 Using Codes During System Design Types of codes Types of codes 4. Significant digit codes: Significant digit codes distinguish items by using a series of subgroups of digits. ZIP codes, for example, are significant digit codes. Significant digit codes Significant digit codes Aisle numberFloor number Section codeBin numberWarehouse location code Sample of a code that uses significant digits to pinpoint the location of an inventory item.

Avicenna System Analysis and Design System Design9 Using Codes During System Design Types of codes Types of codes 5. Derivation codes: Derivation codes combine data from different item attributes, or characteristics, to build the code. Most magazine subscription codes are derivation codes. Derivation codes Derivation codes A magazine subscriber code is derived from various parts of the name and address.

Avicenna System Analysis and Design System Design10 Using Codes During System Design Types of codes Types of codes 6. Cipher codes: Cipher codes use a keyword to encode a number. A retail store, for example, may use a 10-letter word, such as CAMPGROUND, to code wholesale prices, where the letter C represents 1, A represents 2, and so on. Cipher codes Cipher codes 7. Action codes: Action codes indicate what action is to be taken with an associated item. For example, a student records program might prompt a user to enter or click an action code such as D (to display the student's record), A (to add a record), and X (to exit the program). Action codes Action codes

Avicenna System Analysis and Design System Design11 Using Codes During System Design Developing a Code Developing a Code Codes should be easy to remember, decipher, and verify Codes should be easy to remember, decipher, and verify Keep the following suggestions in mind when developing a code: Keep the following suggestions in mind when developing a code: 1. Keep codes concise. Do not create codes that are longer than necessary 2. Allow for expansion. A coding scheme must allow for reasonable growth in the number of assigned codes 3. Keep codes stable. Changes in codes can cause consistency problems and require data updates. During the changeover period, you have to change all the stored occurrence of a particular code and all documents containing the old code, as users switch to the new code

Avicenna System Analysis and Design System Design12 Using Codes During System Design Developing a Code Developing a Code 4. Make codes unique. Codes used for identification purposes must be unique to have meaning 5. Use sortable codes. ensures that data sorts into usable groups. sortable 6. Avoid confusing codes. Avoid allowing both letters and numbers to occupy the same positions within code because some of those are easily confused, like the number 0 and the letter O

Avicenna System Analysis and Design System Design13 Using Codes During System Design Developing a Code Developing a Code 7. Make codes meaningful. Codes must be easy to remember, useful for users, convenient to use, and easy to encode and interpret. Using ENG as the code for the English department is easier to interpret and remember than either XVA or Use a code for a single purpose. Do not use a single code to classify two or more unrelated attributes. 9. Keep codes consistent. For example, if the payroll system already is using two digit codes for departments, do not create a new, different coding scheme for the personal system

Avicenna System Analysis and Design System Design14 Sequence Summary You learned that a code is a set of letters or numbers used to represent data in a system You learned that a code is a set of letters or numbers used to represent data in a system By using codes, you can speed up data entry, reduce data storage space, and reduce transmission time By using codes, you can speed up data entry, reduce data storage space, and reduce transmission time Codes also can be used to reveal or to conceal information Codes also can be used to reveal or to conceal information The main types of codes are sequence codes, block sequence codes, classification codes, alphabetic codes (including category codes, abbreviation codes, and mnemonic codes), significant digit codes, derivation codes, cipher codes, and action codes The main types of codes are sequence codes, block sequence codes, classification codes, alphabetic codes (including category codes, abbreviation codes, and mnemonic codes), significant digit codes, derivation codes, cipher codes, and action codes

Avicenna System Analysis and Design System Design15 Sequence Summary In this Sequence we have In this Sequence we have  Defined the term code  Explained the the importance of codes  described various coding schemes including sequence codes, block sequence codes, classification codes, alphabetic codes (including category codes, abbreviation codes, and mnemonic codes), significant digit codes, derivation codes, cipher codes, and action codes

Avicenna System Analysis and Design System Design16 Reference [1] System Analysis and Design, Sixth Edition Authors: Gary B. Shelly, Thomas J. Cashman and Harry J. Rosenblatt Authors: Gary B. Shelly, Thomas J. Cashman and Harry J. Rosenblatt Publisher: SHELLY CASHMAN SEWIES. Publisher: SHELLY CASHMAN SEWIES.