Unit 7: System Development & Programming Concepts – GCE A/L Exam NOTES | DFD Context Diagram Focus | A/L Computing | Questions and Answers

📘 GCE A/L ICT – UNIT 7

System Development & Programming Concepts

Complete exam-focused notes for Sri Lankan GCE Advanced Level ICT

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🔷 7.1 Introduction to System Development

🔹 What is a System?

A system is a collection of interrelated components working together to achieve a common goal.

📌 Example: School Management System

Component	Description
Inputs	Student data, attendance, marks
Processes	Attendance tracking, marks calculation, report generation
Outputs	Reports, results, certificates

🔹 Types of Systems

Type	Characteristics	Example
Manual Systems	• Paper-based • Human-operated • Slower processing	Attendance register, paper files
Computer-Based Systems	• Automated • Software-driven • Faster & accurate	School ERP, Library Management System

🔹 What is System Development?

The process of creating or modifying a system to meet user requirements and solve problems.

💡 Key Point: System development follows a structured approach called SDLC to ensure quality and efficiency.

🔄 7.2 SDLC – System Development Life Cycle

🔹 Definition

SDLC is a structured, phased process followed to plan, create, test, and deploy an information system.

🔹 The 7 Phases of SDLC

Planning → Analysis → Design → Development → Testing → Implementation → Maintenance

1. Planning
   • Identify the problem/need
   • Conduct feasibility study
   • Define project scope & resources
2. Analysis
   • Study current system
   • Gather user requirements
   • Create Requirement Specification Document
3. Design
   • System architecture
   • Database design (ERD)
   • UI/UX mockups & DFDs
4. Development
   • Actual coding/programming
   • Database implementation
   • Module integration
5. Testing
   • Find & fix bugs
   • Unit testing, system testing
   • User acceptance testing (UAT)
6. Implementation
   • Install & deploy system
   • Train users
   • Data migration
7. Maintenance
   • Fix post-launch issues
   • Apply updates & patches
   • Add new features

🔹 SDLC Example: Library System

Phase	Activity
Planning	Identify need to manage books digitally
Analysis	Interview librarians, list requirements
Design	Create database schema + UI wireframes
Development	Code the system in chosen language
Testing	Test borrowing, returning, fine calculation
Implementation	Install in library, train staff
Maintenance	Fix bugs, add e-book feature later

🎯 Exam Tip: Memorize the 7 phases IN ORDER. A common 4-mark question asks you to list them sequentially.

📊 7.3 Feasibility Study (TEOS)

🔹 Purpose

❓ Key Question: "Is this system worth developing?"
Feasibility study evaluates if the project is practical, affordable, and achievable.

🔹 Types of Feasibility (TEOS)

Type	Key Question	Example
Technical 🔧	Do we have the technology & skills?	Need mobile app developers, cloud server
Economic 💰	Do benefits > costs?	Cost: Rs.500k | Benefit: Rs.1M → ✅ Feasible
Operational 👥	Will users accept & use it?	Can teachers learn the new system easily?
Schedule 📅	Can it be done on time?	Can we finish before next academic year?

🔹 Economic Feasibility Formula

Feasible if:
Expected Benefits > Development + Operational Costs

Example Calculation:

• 💸 Development Cost: Rs. 500,000
• 📈 Annual Benefit: Rs. 300,000 × 4 years = Rs. 1,200,000
• ✅ Net Gain: Rs. 700,000 → Project is feasible!

🎯 Exam Trick: If asked "Explain feasibility study", use the TEOS structure + one calculation example for full marks.

🔷 7.4-7.5 Data Flow Diagrams (DFD)

🔹 What is a DFD?

A Data Flow Diagram is a graphical representation showing how data moves through a system – from input, through processes, to output.

🔹 DFD Symbols (MEMORIZE FOR EXAMS)

Symbol	Name	Meaning	Example
○ Circle	Process	Transforms input to output	"Calculate Marks"
➜ Arrow	Data Flow	Movement of data	"Student Details"
▭ Rectangle	External Entity	Source/destination outside system	Student, Admin, Bank
▭▭ Open Rectangle	Data Store	Where data is stored	Database, File

🔹 Levels of DFD

🎯 Exam Focus: You MUST know Context Diagram (Level 0) in detail!

• Level 0 (Context Diagram): Entire system as ONE process + external entities
• Level 1 DFD: Breaks system into major sub-processes
• Level 2+ DFD: Further decomposition of processes

🔹 Context Diagram – EXAM CRITICAL

✅ What it Shows:

• The whole system as a single process
• All external entities interacting with it
• Data flows between entities and system

🔹 How to Draw: 4 Simple Steps

1. Identify the System
   Example: [ Student Registration System ]
2. Identify External Entities
   Example: [Student] [Admin] [Examination Dept]
3. Map Inputs & Outputs

   Entity	Input to System	Output from System
   Student	Registration details	Confirmation SMS
   Admin	Course data	Enrollment reports

4. Draw Labeled Arrows
   [Student] → Registration Details → [System]

🔹 Critical Rules (MCQ Gold)

✔ MUST DO:

• Only ONE process box (the whole system)
• NO internal processes or data stores
• ALL external entities must be shown
• EVERY arrow must have a clear label
• Arrows show direction of data flow

❌ AVOID THESE MISTAKES:

• Drawing multiple process circles ❌
• Adding database symbols ❌
• Unlabeled arrows ❌
• Missing key entities ❌

🧮 7.6 Algorithms & 7.7 Flowcharts

🔹 Algorithm Definition

An algorithm is a finite, step-by-step procedure written in simple language to solve a specific problem.

🔹 Characteristics of a Good Algorithm

Characteristic	Meaning
Finite	Must have a definite end point
Clear	Each step must be unambiguous
Logical	Steps must follow correct order
Effective	Must solve the problem correctly
Input/Output	Must have defined inputs & outputs

🔹 Algorithm Writing Rules (Exam)

• ✓ Use numbered steps (1, 2, 3...)
• ✓ Use simple, plain English (no code syntax)
• ✓ Start with INPUT and end with STOP/END
• ✓ Use IF-THEN-ELSE for decisions
• ✓ Keep each step atomic (one action per step)

🔹 Example: Find Largest of 3 Numbers

1. INPUT A, B, C 2. IF A > B AND A > C THEN 3. PRINT "Largest is", A 4. ELSE IF B > C THEN 5. PRINT "Largest is", B 6. ELSE 7. PRINT "Largest is", C 8. END IF 9. STOP

🔹 Flowchart Definition & Symbols

A flowchart is a graphical representation of an algorithm using standardized symbols.

Symbol	Name	Purpose
⬭ Oval	Terminal	Start/End points
▭ Rectangle	Process	Calculation/action step
◇ Diamond	Decision	Yes/No condition check
➜ Arrow	Flow Line	Direction of execution
▱ Parallelogram	Input/Output	Read data / Display result

💡 Exam Tip: Always label decision branches with "Yes/No"! Missing labels cost marks.

💻 7.8 Programming Concepts

🔹 Variables & Data Types

Named storage locations that hold data values.

Example:
int age = 20;
String name = "Student";
boolean isActive = true;

🔹 Basic Data Types

Data Type	Stores	Example
Integer	Whole numbers	25, -10, 0
Float/Double	Decimal numbers	3.14, -0.5
String	Text characters	"Hello", "A/L 2026"
Boolean	True/False values	true, false

🔹 Operators

🔢 Arithmetic: + - * / % ⚖️ Comparison: == != > < >= <= 🔗 Logical: AND(&&), OR(||), NOT(!) 📝 Assignment: = += -=

🔹 Control Structures (CORE CONCEPT)

1️⃣ Sequence

Statements executed in order, one after another.

INPUT name PRINT "Hello", name CALCULATE total PRINT total

2️⃣ Selection (Decision)

Execute different code based on a condition.

IF-ELSE Example:
IF marks >= 50 THEN PRINT "PASS" ELSE PRINT "FAIL" END IF

3️⃣ Iteration (Loop)

Repeat a block of code multiple times.

FOR Loop Example:
FOR i = 1 TO 10 STEP 1 PRINT i NEXT i

🧪 7.9 Testing & Debugging

🔹 Testing vs Debugging

Testing	Debugging
• Finding errors/bugs • Done BEFORE release • Uses test data	• Fixing identified errors • Done AFTER testing • Requires code analysis

🔹 Types of Testing

Type	Purpose	Example
Unit Testing	Test individual modules/functions	Test "calculateTotal()" function alone
System Testing	Test complete integrated system	Test full library borrowing workflow
Acceptance Testing	User validates system meets needs	Librarian tests before going live

🔹 Test Data Types (EXAM FAVORITE)

Type	Example (marks 0-100)	Purpose
Normal Data ✅	50, 75, 90	Verify expected valid inputs work
Boundary Data 🎯	0, 100	Test edge limits of valid range
Invalid Data ❌	-10, 150, "abc"	Check error handling & validation

🔹 Input Validation Techniques

📏 Range Check: 0 ≤ marks ≤ 100 ✉️ Format Check: email@domain.com 🔢 Type Check: isNumeric(phone) ✅ Presence Check: name != empty 🔐 Length Check: password ≥ 8 chars

🚀 7.10 Implementation Methods

🔹 When to Use Each Method

Method	Best For	Pros	Cons
Direct (Big Bang)	Small, low-risk systems	• Fast • Low cost	• High risk • No fallback
Parallel	Critical systems (Banks, Hospitals)	• Safe • Easy rollback	• Expensive • Double work
Pilot	Large organizations (Test in one branch)	• Low risk • Real-world feedback	• Slow rollout • Branch comparison issues
Phased (Modular)	Complex modular systems	• Manageable • Early benefits	• Integration challenges • Longer timeline

🎯 Exam Answer Template:
"For a banking system, I would recommend Parallel Implementation because:
✓ Critical data must not be lost
✓ Old system can run as backup
✓ Users can be trained gradually
✓ Errors can be fixed without stopping service"

📄 Pass Paper Questions & Model Answers

🔹 Question 1 (2 Marks)

Define SDLC.

✅ Model Answer:
SDLC (System Development Life Cycle) is a structured, phased process used to plan, create, test, deploy, and maintain information systems through stages such as planning, analysis, design, development, testing, implementation, and maintenance.

🔹 Question 2 (4 Marks)

List 4 phases of SDLC.

✅ Model Answer:
Planning Analysis Design Implementation

🔹 Question 3 (2 Marks)

What is a feasibility study?

✅ Model Answer:
A feasibility study is the process of evaluating whether a proposed system is practical, affordable, technically achievable, and worth developing before committing resources to the project.

🔹 Question 4 (6 Marks) – Context Diagram

Draw a context diagram for a Library Management System.

✅ Model Answer Structure:

1. Center: [ Library Management System ]
2. External Entities: Member Librarian Supplier
3. Data Flows:
   • Member → Book Request → System
   • System → Borrow Confirmation → Member
   • Librarian → Update Catalog → System
   • System → Overdue Report → Librarian

✨ Must have: 1 process, labeled arrows, all entities, no data stores

🔹 Question 5 (2 Marks)

State two programming control structures.

✅ Model Answer:
Selection (IF-ELSE) Iteration (FOR/WHILE loops)

🌟 Beginner-Friendly Quick Review

🔹 Super Simple Summary Table

Term	Super Simple Meaning	Memory Trick
SDLC	Build → Test → Use → Maintain	🔄 4-step cycle
DFD	How data moves	➜ Arrow diagram
Algorithm	Step-by-step problem solver	📋 Recipe
Flowchart	Picture of an algorithm	🖼️ Visual steps
Testing	Finding bugs before launch	🔍 Check first
Debugging	Fixing bugs after testing	🔧 Repair mode
Direct Changeover	Switch old→new in one day	⚡ Fast but risky
Parallel	Run old+new together	🛡️ Safe but costly

🔹 Exam Keyword → Answer Trick

🔍 Question Keyword	✅ Write This
"daily transactions", "billing", "ATM"	TPS
"reports", "summary", "analysis"	MIS
"decision", "strategy", "future plan"	DSS
"step by step", "cannot go back"	Waterfall
"flexible", "user feedback", "changing"	Agile
"fast", "prototype", "ready-made"	RAD

🧠 FINAL MASTER TIP

👉 For DFD Questions:
✓ Draw neatly with pencil & ruler
✓ Label EVERY arrow with data name
✓ Use correct symbols ONLY
✓ Keep system as ONE process box

👉 For Algorithm Questions:
✓ Start with INPUT, end with STOP
✓ Use numbered steps
✓ Test your logic with sample values!