Program Construction Methodology
Overview
Section titled “Overview”Program Construction Methodology is a systematic approach to building software programs. It consists of two main components:
- Overall System Design
- Software Development
Important Note: Program construction is the entire journey, while programming is just a part of it.
Prerequisites: Essential Steps Before Development
Section titled “Prerequisites: Essential Steps Before Development”Before beginning any software project, the following steps must be completed:
- System Requirements Analysis
- System Requirements Specification
- System Architecture Design
- System Validation
Types of Requirements
Section titled “Types of Requirements”Requirements are broadly classified into two main categories:
Functional Requirements
Section titled “Functional Requirements”Functional requirements describe what a system must do. They specify the actual functions and behaviors the system needs to have to meet user needs.
Two Approaches to Define Functional Requirements
Section titled “Two Approaches to Define Functional Requirements”1. Based on Functionality (Specific Functions)
Examples for an Online Banking System:
- The system must allow users to transfer money between accounts
- The system must generate monthly account statements
- The system must calculate interest on savings accounts
- The system must allow password changes
2. Based on Behavior (How the System Responds)
Input/Output Behavior Examples:
- Input: User enters correct PIN → Output: ATM displays main menu
- Input: Invalid login attempt 3 times → Output: System locks account for 30 minutes
- Input: Account balance below $100 → Output: System sends low balance alert
- Input: User clicks “Forgot Password” → Output: System sends reset email
Non-Functional Requirements
Section titled “Non-Functional Requirements”Non-functional requirements specify how a system should perform. They are commonly referred to as “-ilities”.
Examples of Non-Functional Requirements:
Section titled “Examples of Non-Functional Requirements:”- Reliability - How dependable is the system?
- Scalability - Can it handle growth?
- Usability - How easy is it to use?
- Maintainability - How easy is it to modify?
- Security - How well protected is it?
- Portability - Can it work on different platforms?
- Availability - How often is it operational?
Characteristics of Non-Functional Requirements
Section titled “Characteristics of Non-Functional Requirements”Non-functional requirements are often:
- Subjective - “The system should be user-friendly”
- Ambiguous - “The system should be fast”
- Conflicting - May contradict each other
Documentation Requirements
Section titled “Documentation Requirements”Requirements must be documented to be easily understood by:
- Non-technical readers (customers)
- Technical readers (software developers)
Comparison: Functional vs Non-Functional Requirements
Section titled “Comparison: Functional vs Non-Functional Requirements”| Aspect | Functional Requirements | Non-Functional Requirements |
|---|---|---|
| Objective | Describe what product does | Describe how product works |
| End Result | Define product features | Define product properties |
| Focus | On user requirements | On user expectations |
| Documentation | Captured in Use Cases | Captured as quality attributes |
| Origin Type | Defined by user (mostly) | Defined by developers/experts |
| Testing | • Component Testing • Module Testing • API Testing • UI Testing | • Performance Testing • Usability Testing • Security Testing • Load Testing |
This guide provides a structured approach to understanding and implementing program construction methodology for successful software development projects.