Unit 2: System design
System Analysis & Design notes · PTU syllabus (BSIT403/BSBC301)
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Unit summary
Design turns requirements into a blueprint for building the system. This unit covers the process and stages of system design, input and output design, file design, documentation — user manual, design documentation and training manual — and case study techniques in system design.
After this unit you can
- Explain the stages of system design
- Design inputs, outputs and files
- Prepare system documentation
- Apply design techniques to a case study
PTU syllabus topics
- Process and stages of systems design
- input/output and file design
- documentation (user manual, design documentation, training manual)
- case study techniques in system design
Input design
Forms, screens, validation
Output design
Reports, dashboards
File and database design
Tables, keys
Process design
Programs, logic
Documentation
User, design and training manuals
Topic 1
Process and stages of system design
- 1Logical design
What the system must do: outputs, inputs, data stores, procedures (DFDs, ER)
- 2Physical design
How it is done: hardware, software, screens, database tables, programs
- 3Architectural design
Modules and their interfaces (structure chart)
- 4Detailed design
Algorithms, data structures, validation rules for each module
- Design objectives: practical, efficient, cost-effective, flexible, secure and easy to use.
- Design tools: structure charts, HIPO (hierarchy plus input–process–output), flowcharts, pseudocode, ER diagrams, screen mock-ups.
Topic 2
Input design
- Objectives: accurate, easy and quick data entry with minimum errors.
- Capture data once at the source
- Avoid re-entry
- Use codes and drop-downs
- Course code instead of typing names
- Validate input
- Type, range, format, check digits, mandatory fields
- Design clear forms
- Logical order, labels, defaults, help text
- Choose input media
- Keyboard, barcode, OCR, mobile, biometric
Example
Admission form: roll number auto-generated, date picked from a calendar, category from a drop-down, mobile number checked for 10 digits starting 6–9, marks between 0 and 100.
Topic 3
Output design
- Objectives: right information, to the right person, at the right time, in the right format.
External
Goes outside the organisation
Fee receipts, mark sheets
Internal
Used within the organisation
Attendance reports
Turnaround
Sent out and returned with data
Utility bill with a payment slip
Screen and interactive
Displayed on screen
Dashboards
Exception
Only unusual items
List of students below 75% attendance
- Guidelines: meaningful titles and dates, totals and subtotals, charts where helpful, avoid clutter.
Topic 4
File design
- File design decides how data is organised and stored.
- Master file
- Permanent data — student master
- Transaction file
- Day-to-day events — fee payments
- Table file
- Reference values — fee structure
- Report file
- Formatted output awaiting printing
- Backup file
- Copy for recovery
- Archival file
- Old records kept for history
Sequential
Records read in order
Batch processing such as payroll
Direct (random or hashed)
Record found directly by key
Online enquiries, reservations
Indexed sequential
Index for direct access plus sequential order
Both — e.g., library catalogue
- Record design: fields, size, type, key field and validation rules; today largely replaced by database table design with normalisation.
Topic 5
Documentation
User manual
End users
Getting started, step-by-step procedures, screenshots, error messages, FAQs
Design documentation
Developers and maintainers
DFDs, ER diagrams, data dictionary, module specifications, program listings, test plans
Training manual
Trainers and new users
Lessons, exercises, practice data, assessments
- Other documents: system proposal, requirements specification (SRS), operations manual for computer staff (backups, schedules).
- Good documentation is accurate, up to date, clear, indexed and version-controlled.
Topic 6
Case study techniques in system design
- 1Study the case
Organisation, problems and objectives
- 2Identify requirements
Inputs, outputs, users, volumes
- 3Draw models
Context diagram, level-1 DFD, ER diagram
- 4Design
Input screens, output reports, files or tables
- 5Evaluate
Alternatives, costs, benefits; recommend
Example
Case: hostel management for 400 students. Inputs — room allotment form, mess bills; outputs — room list, monthly dues, defaulters (exception report); files — student master, room master, payment transactions; design — web forms with validation and SMS alerts for dues.
Key terms
- Logical design
- Description of what the system will do
- Physical design
- Description of how the system will be built
- Input validation
- Checking data for errors at entry
- Master file
- File of permanent reference data
- User manual
- Guide explaining how to use the system
Quick revision
- Logical and physical design; architectural and detailed design; design tools.
- Input design goals and validation checks.
- Output types: external, internal, turnaround, interactive, exception.
- Files: master, transaction, table, report, backup; sequential, direct, indexed.
- User manual, design documentation, training manual; case study steps.
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.Distinguish logical and physical design.
- Q2.State three objectives of input design.
- Q3.What is a turnaround document?
- Q4.Distinguish master and transaction files.
- Q5.What does a training manual contain?
- Q6.What is an exception report?
Long-answer questions
- Q1.Explain the process and stages of system design.
- Q2.Explain input and output design with examples.
- Q3.Explain file design and file organisations.
- Q4.Explain the types of system documentation.
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