Unit 1: System Development Life Cycle
System Analysis & Design notes · PTU syllabus (BSIT403/BSBC301)
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Unit summary
Every information system is planned, analysed, designed, built and maintained through a disciplined life cycle. This unit covers the definition, characteristics, elements and types of systems, the phases of the system development life cycle, information gathering tools, structured analysis tools and the role of the system analyst.
After this unit you can
- Define a system and describe its characteristics, elements and types
- Explain the phases of the SDLC
- Use information gathering and structured analysis tools
- Describe the role and qualities of a system analyst
PTU syllabus topics
- System definition
- characteristics
- elements and types
- phases of SDLC
- information gathering tools
- structured analysis tools
- role of the system analyst
- 1
Preliminary investigation
Is there a problem worth solving?
- 2
Feasibility study
Technical, economic, operational
- 3
System analysis
Requirements, DFDs
- 4
System design
Input, output, files, database
- 5
Development and testing
- 6
Implementation
- 7
Maintenance
Topic 1
System: definition and characteristics
- System: an organised set of interrelated components working together towards a common goal — e.g., a college admission system, a payroll system, the human body.
- Organisation
- Components arranged in a structure that achieves objectives
- Interaction
- Components work with each other (admissions with accounts)
- Interdependence
- One part depends on another; output of one is input to another
- Integration
- Parts combine into a whole
- Central objective
- A common goal that all parts serve
Topic 2
Elements of a system
- 1
Inputs
Data and resources entering the system
- 2
Processor
Operations that transform inputs into outputs
- 3
Outputs
Results such as reports, bills, results
- 4
Control
Decision-making that guides the system
- 5
Feedback
Output compared with standards and fed back to control
- 6
Environment and boundaries
Everything outside that affects it, separated by a boundary
- 7
Interface
Points where the system meets other systems
Example
Online fee system: input — student ID and amount; processor — validation and payment gateway; output — receipt; control — finance rules; feedback — daily reconciliation report; environment — bank, students, university; interface — payment gateway API.
Topic 3
Types of systems
Physical or abstract
Tangible equipment, or ideas and models
Computer hardware; a payroll formula
Open or closed
Interacts with environment, or isolated
Business firm; a sealed chemical reaction
Deterministic or probabilistic
Predictable output, or uncertain output
Calculator; weather forecasting
Man-made information systems
TPS, MIS, DSS
Billing (TPS), monthly sales reports (MIS), what-if planning (DSS)
- Information systems by level: transaction processing systems (operations), management information systems (middle management), decision support systems and executive support systems (top management).
Topic 4
Phases of the system development life cycle
- 1. Preliminary investigation: Identify the problem and test feasibility
- 2. System analysis: Study the current system and determine requirements
- 3. System design: Plan the new system: input, output, files, processes
- 4. Development: Write and unit-test programs
- 5. Testing: Integrate and test the whole system
- 6. Implementation: Convert, train users and go live
- 7. Maintenance: Correct, adapt and improve over time
- Technical feasibility
- Can it be built with available technology and skills?
- Economic feasibility
- Do benefits exceed costs (cost–benefit analysis)?
- Operational feasibility
- Will users accept and use it?
- Schedule feasibility
- Can it be done in time?
- Legal feasibility
- Does it comply with laws and contracts?
Topic 5
Information gathering tools
Review of records and documents
Understanding current forms, reports, policies
Records may be outdated
On-site observation
Seeing how work is actually done
People behave differently when watched
Interviews
In-depth opinions of key users
Time-consuming; interviewer bias
Questionnaires
Many users spread across locations
Low response; no follow-up
Joint application development (JAD) sessions
Agreement among users and developers
Needs a skilled facilitator
Example
For a library system, the analyst reviews issue registers, observes the counter at peak hours, interviews the librarian and sends a questionnaire to 200 students.
Topic 6
Structured analysis tools
- Data flow diagram (DFD): shows how data moves through processes, stores and external entities; drawn in levels (context diagram as level 0, then level 1, level 2).
- External entity (rectangle)
- Source or destination of data — Student
- Process (circle or rounded box)
- Transforms data — Issue book
- Data store (open rectangle)
- Stored data — Books file
- Data flow (arrow)
- Movement of data — Issue request
- Data dictionary: a catalogue defining every data element, flow and store — name, type, size, range and where used.
- Decision table: lists conditions and actions in a grid for complex rules.
- Decision tree: shows the same rules as branches.
- Structured English: describes process logic in plain language with IF–THEN–ELSE and loops.
| Decision table: library fine | Rule 1 | Rule 2 | Rule 3 |
|---|---|---|---|
| Returned late? | No | Yes | Yes |
| More than 10 days late? | — | No | Yes |
| Action | No fine | Rs 5 per day | Rs 5 per day + notice |
Topic 7
Role of the system analyst
Change agent
Introduces and manages change in the organisation
Investigator and monitor
Finds causes of problems and tracks progress
Architect
Designs the logical and physical structure
Motivator, psychologist and salesperson
Wins user acceptance and sells the idea
- Qualities: analytical and problem-solving ability, communication, business knowledge, technical knowledge, interpersonal skills, honesty and patience.
Key terms
- System
- Set of interrelated components working towards a goal
- SDLC
- Phased process for developing information systems
- Feasibility study
- Assessment of whether a system is worth building
- DFD
- Diagram showing data movement through a system
- Data dictionary
- Repository of definitions of data elements
Quick revision
- Characteristics: organisation, interaction, interdependence, integration, central objective.
- Elements: input, process, output, control, feedback, environment, boundary, interface.
- Types: physical/abstract, open/closed, deterministic/probabilistic; TPS, MIS, DSS.
- SDLC phases; feasibility types.
- Records, observation, interviews, questionnaires, JAD; DFD, data dictionary, decision tables and trees, structured English; analyst roles.
Important exam questions
Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).
Short-answer questions
- Q1.Define a system.
- Q2.What is feedback in a system?
- Q3.Distinguish open and closed systems.
- Q4.Name the types of feasibility.
- Q5.State two advantages of questionnaires.
- Q6.What is a context diagram?
Long-answer questions
- Q1.Explain the characteristics and elements of a system.
- Q2.Explain the phases of the SDLC.
- Q3.Explain information gathering tools with their merits and limitations.
- Q4.Explain structured analysis tools and the role of the system analyst.
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