code development code development for end user systems

Code Development

Code development for end user systems

Program Architecture

The organization of code components

The objective of system architecture is to simplify maintenance by

putting code together that will be changed at the same time

Architectural Philosophies

Requirements Driven Data Driven Dialog Driven Event Driven

Coding Standards

StructuredLimit control structures to sequence,

iteration, and selection Event Driven

Interactive systems driven by user actions

Object orientedEncapsulate data and code into objects

that can be called independently

Good Code Maintenance is 80% of the cost of a

large system. Instructions that will be changed

together located together. Errors and bugs isolated.

Traditional Design

Traditional Life Cycle ApproachFormal MethodologiesCASE ToolsPurchased Systems

New ApproachesRADEvolutionary CodeGUI designObject Oriented Design

Good Practice: Loose Coupling

Associations among code modules

Data passes only data Control passes data and control

codes Stamp passes information from

the structure of the data Hybrid one module changes the

code in another

Good Practice: Tight Cohesion

Functions done by one code module.

A module is a set of code statements that is called and executed together. A cohesive module executes only statements that always go together.

Typical Modules

Modules in identified files Macros and functions Forms, Reports and Queries Objects

Programming Principles

KISS (Keep it Simple, Stupid)Volatility

Prototyped code will be revised frequently. Simple solutions are much better than elegant ones that are hard to understand.

Clarity over EfficiencyEUC systems are usually elective and not run as production code.


Code should be written to be readGood communication principles

White spaceBoxesIndentationExplain complex logic

Modular constructionVery simple control structures

Mnemonic variables


Minimize external documentationDocument the objective rather than the

procedure. The next programmer can find his own solution too.

Include descriptive and complete title lines

Include an initial statement of program purpose

Line comments hard to maintain


Fully document data filesUse labels and file descriptionsUse original common data sources where

possibleCreate as few original data tables as

possibleDocument edits and modifications


Retain natural documentationKeep instructional memos and notes in

fileDocument objectives so that modules

can be reprogrammed as needed

References

Weinberg, ‘Prototyping and the SDLC’, J Info Systems Mgt, 1991.Chen, Nunamaker, Weber, ‘CASE: present status and future directions’,

Database, 1989

code development code development for end user systems

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