How to design conventional components - Program Design Language and Comparison of Design Notation

Conventional component level design requires the representation of data structures, interfaces, and algorithms for a program module. The designer uses one of a number of design notations that represent component level detail in either graphical, tabular, or text based formats.

PROGRAM DESIGN LANGUAGE
Program design language is also called pseudo code. In this, vocabulary of one language and overall syntax of another language is used. Program design language(PDL) is used as a generic reference for a design language.
The difference between a PDL and a real programming language lies in the use of narrative text embedded directly within PDL statements.
- PDL cannot be complied.
- Tools can translate PDL into a programming language.
- These tools also produce nesting maps, design operation index, cross reference tables and other information.
- PDL may be simple transposition of a language.
- Basic PDL syntax should include constructs for component definition, interface description, data declaration, block structuring, condition and repetition constructs.
- PDL can be extended to include keywords for multitasking, interrupt handling, interprocess synchronization.

COMPARISON OF DESIGN NOTATION
- Design notation leads to procedural representation which is easy to understand and review.
- Design notation should enhance "code to" ability.
- Design representation must be easily maintainable so that design always represents the program correctly.
- PDL offers the best combination of characteristics.
- However, it does not follow that other design notations are inferior.
- Activity diagrams and flowcharts provides a perspective on control flow that many designers prefer.