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Chapter 14 – Data Flow Diagrams
14.5. Exercises
1.
Read the following description of a system and look at the Level 1 DFD which an inexperienced
trainee analyst has drawn to represent it. What is wrong with it? Redraw it correctly.
A customer places an order with Victory Publishing for some books. The order is accepted by the
Sales Order Processing Department. An invoice is printed and sent to the customer. A despatch note
is printed and sent to the warehouse. The goods and the despatch note are sent to the customer from
the warehouse. A second copy of the invoice is sent to the Accounts Department.
Customer
Invoice
Order
Process
order
Accounts
Department
Despatch note
Goods,
despatch note
Warehouse
(2 marks)
2.
A student can register by mail for a college course by submitting a registration form with their name,
ID number and the numbers of the courses they wish to take. The system verifies that the course is
not full and enrols the student on each course for which a place is still free. The course file and
student master files are updated and a confirmation letter is sent to the student to notify them of their
acceptance or rejection for each requested course.
Draw (i) a Level 0 DFD
(3 marks)
(ii) a Level 1 DFD of the above system.
3.
(5 marks)
A payroll system works as follows:
At the end of each month, the Payroll Department is informed of any holidays, unpaid leave,
maternity leave or sick days taken by any employees. Payroll data is entered and validated, valid
transactions are stored on a transaction file and invalid transactions are printed in an error report.
Payroll calculations are carried out using the transaction file and the employee master file, which is
updated with year-to-date figures. Payslips are sent to the employees, funds transferred electronically
to the employees’ bank accounts and the Accounts system is sent the data necessary to update the
ledgers.
(i)
Identify the external entities in the above description.
(ii) Draw
4.
(3 marks)
(a) a Level 0 DFD
(3 marks)
(b) a Level 1 DFD of the above system.
(5 marks)
What is the purpose of a Level 0 DFD?
(2 marks)
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