1. Structure Charts

2. Structure Chart is an important tool for showing relationship between the modules of a computer program in SSAD (Structured Systems Analysis and Design) [Page-Jones, 1988].

3. Structure Charts
Use of Structure Charts
Symbols
How to create

4. Structure Chart Use
Describe functions and sub-functions of each part of system (in more detail than a DFD)
In contrast to flow chart, Structure Charts does not represent sequence of execution.
However, this problem can be solved by following the rule of “reading from left to right”

5. Structure Chart Use
Show relationships between common and unique modules of a computer program
Hierarchical, Modular structure
Each layer in a program performs specific activities
Each module performs a specific function

6. Structure Chart Symbols
Structure Chart symbols represent
Modules (sequential logic)
Conditions (decision logic)
Loops (iterative logic)
Data couples
Control couples

7. Structure Chart Symbols Module
Control Modules
Library Modules
Modules is a program or subroutine containing sequential logic: a form of binary circuit design that employs one or more inputs and one or more outputs, whose states are related by defined rules.

8. Structure Chart - Module
Control Modules (mainline) branch to sub-modules
Library modules are reusable and can be invoked from more than one Control Module elsewhere in the system

9. Structure Chart Symbols
Module Invocation Arrow
(only from main to sub)
Data Flow Arrow / data couple
Control Flow Arrow/ control couple

10. Structure Chart
Module Invocation Arrow

11. Structure Chart - Data Couple
Arrow with an empty circle
Shows the data one module passes to another

12. Structure Chart - Control Couple
Arrow with filled circle
Shows a message (flag) which one module sends to another
Module uses a flag to signal a specific condition or action to
another module

13. Structure Chart Symbols
Conditions (decision logic)
A line with a diamond
Indicates that a control module determines which
subordinate module will be invoked

14. Structure Chart - Condition
One of these three subordinate module will be executed based on the output from the control module (sort inventory parts)

15. Structure Chart Symbols
Loops(iterative logic)
Can only be drawn in module invocation arrow. Indicating that the control module actions will be repeated until a certain flag or user input.

16. Structure Chart - Loop A curved arrow representing a loop
One or more modules are repeated

17. Structure Chart for Calculate Pay Amount Routine

18. Structure Chart for Entire Calculate Payroll Program

19. Steps in drawing a structure chart
Review the DFDs and object models
Identify modules and relationships
Add couples, loops, and conditions
Analyze the structure chart, the DFDs, and the data dictionary

20. Summary - Structure Charts
Show the relationships among program modules
Structure Chart consists of:
Modules - Related program code organized into small units that are easy to understand and maintain
Data couples - Data passed between modules
Control couples - Data passed between modules that indicates a condition or action to another module (e.g. End of File)
Conditions - determines what subordinate module a control module will run
Loops - Indicates one or more subordinate modules are repeated
Structure Charts are based on the DFD and Data Dictionary

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