Program Construction Methodology

Overview

Program Construction Methodology is a systematic approach to building software programs. It consists of two main components:

1. Overall System Design
2. Software Development

Important Note: Program construction is the entire journey, while programming is just a part of it.

Prerequisites: Essential Steps Before Development

Before beginning any software project, the following steps must be completed:

1. System Requirements Analysis
2. System Requirements Specification
3. System Architecture Design
4. System Validation

Types of Requirements

Requirements are broadly classified into two main categories:

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

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

Non-functional requirements specify how a system should perform. They are commonly referred to as “-ilities”.

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

Non-functional requirements are often:

1. Subjective - “The system should be user-friendly”
2. Ambiguous - “The system should be fast”
3. Conflicting - May contradict each other

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

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

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This guide provides a structured approach to understanding and implementing program construction methodology for successful software development projects.