Level 0 DFD (Context Diagram – ATM System)
This shows the ATM System as a single process with external entities.
Entities & Flows:
- Customer → inserts Card & PIN, Transaction Request → ATM System
- ATM System → provides Cash, Receipt, Account Info → Customer
- Bank Database ↔ verifies PIN, Account Details, Balance ↔ ATM System
- Bank Server ↔ processes Fund Transfer / Withdrawal / Deposit ↔ ATM System
Diagram Structure (Level 0)
Customer --------------------->
\
\ +-------------------+
-----> | |
Bank Database <-----------------> | ATM System |
| |
Bank Server <-----------------> +-------------------+
Customer <-----------------------
Level 1 DFD (Decomposition of ATM System)
Now we break down the ATM System into sub-processes.
Processes in ATM System:
- Authenticate User → Customer enters card & PIN, verified with Bank Database.
- Select Transaction → Options: Withdraw, Deposit, Balance Inquiry, Fund Transfer.
- Process Transaction → Executes transaction via Bank Server.
- Dispense Cash / Receipt → Dispenses cash or prints receipt.
- Update Account → Updates balance in Bank Database.
Data Stores:
D1: Customer Account Database (account details, balance, PIN).
D2: Transaction Log Database (history of withdrawals, deposits, transfers).
Diagram Structure (Level 1)
Customer ---> [1. Authenticate User] <----> Bank Database
|
v
Customer ---> [2. Select Transaction]
|
v
[3. Process Transaction] <----> Bank Server
|
v
[4. Dispense Cash / Receipt] ---> Customer
|
v
[5. Update Account] <----> Bank Database
Data Stores:
D1: Customer Account Database
D2: Transaction Log Database
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