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Uploaded byramya marichamy
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Design notation

This document discusses various design notations that can be used at different levels of software design, including: - Data flow diagrams, structure charts, HIPO diagrams, pseudo code, and structured flowcharts, which can be used for external, architectural, and detailed design specifications. - Data flow diagrams use nodes and arcs to represent processing activities and data flow. Structure charts show hierarchical structure and interconnections. HIPO diagrams use a tree structure. - Other notations discussed include procedure templates for interface specifications, pseudo code for algorithms and logic, and decision tables for complex decision logic.

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DESIGN NOTATION PRESENTED BY M.RAMYA. M.sc (CS&IT), NADAR SARASWATHI COLLEGE OF ARTS & SCIENCE, THENI.
INTRODUCTION • Good notation can clarify the interrelationships and interaction of interest. • Three level of design specifications:  External design specification  Architectural design specification  Detailed design specification
• Notation used to specify the external characteristic , architectural structure and processing details of a software system include:  Dataflow diagram  Structure charts  HIPO diagrams  Procedure specification  Pseudo code Structured flow charts
DATA-FLOW DIAGRAMS • Dataflow diagrams are directed graphs in which the nodes specify processing activities and the arcs specify the data items transmitted between processing nodes. • Dataflow diagram can be expressed using informal notation can be used to processing nodes , data sources , data sinks and data stores.
• Dataflow diagrams are excellent communicating with customer during requirements and analysis. • There are also used for representation of external and top level internal design specifications
Comput e C Comput e E Comput e D Transfo rm B Transfo rm A Input A Input B Operator Input Y Reference Data X Operator Input Z Output E Output D B’ A’ C AN INFORMAL DATA FLOW DIAGRAM OR “BUBBLED CHART”
STRUCTURED CHARTS • Structure chats are used to architectural design to document hierarchical structure , parameters and interconnection in a system . It differs from a flowchart in two ways:  Structured chart has know decisions boxes.  Sequential ordering of tasks
A ED H CB GF 1 2 3 4 5 6 7 8 INDICATE REPETITION FORMAT OF A STRUCTURE
HIPO DIAGRAMS • HIPO diagram(Hierarchy-process-input-output) were developed at IBM as design representation schemes for top- down software developed and external documentation aids for products. • HIPO diagram contains a visual table of contents, a set of overview diagram and set detail diagrams , it contains of a tree structured .
PROCEDURE TEMPLATE • The format of a procedure interface specification of architectural design , only information in level 1 need to supplied . The information on levels 2,3, and 4 can be included in successive steps. • It provides initial architectural design , specification of side effects , exception handling , processing algorithms and data representation.
PSEUDO CODE NOTATION • Pseudo code notation can be used in both the architectural and detailed design phases . • The designer describes system characteristics using short , concise , that are structured by keywords such as If-Then- Else , While-Do and End. • Pseudo code can replace flowcharts and reduce the amount of external documentations required to describe system.
STRUCTURED FLOWCHARTS • Flowcharts means are specifying and documenting algorithmic detailed in a software system. • Flowchart interoperate rectangular boxes for actions , diamond shaped boxes for decisions , directed arcs for interconnections for boxes. • Single entry , single exit allows hierarchical nesting of structured flowchart to design in top-down fashion.
S1; S2; P S F T WHILE P DO S; BASIC FORMS FOR STRUCTURED FLOWCHARTS
DECISION TABLES • Decision tables can be used to specify complex decision logic in a high level software specification. • There are useful for specifying algorithmic logic during detailed design. • Several preprocessor packages are available to translate decision tables into COBOL.
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