Computer Studies

Systems Development

Systems Development

• Systems investigation• Systems analysis• Systems design• Systems implementation• Systems testing • Systems evaluation

System Analysis and Design

• System Analysts ($$$$$$$$$$)• EXAMINING business situation• BETTER procedures and methods

Case Study

• 97-AL-Comp Stud II-14• A wholesale company recently decided to comp

uterize its existing manual system. The company had previously not used computers at all.

Case Study (cont’)

• Peter, with three years’ experience as a programmer, was recruited to carry out the computerization of the system. Besides programming, Peter is also knowledgeable about the latest microcomputers on the market and commonly-used software packages, such as word processors and spreadsheets. He recommended that the company should buy a number of microcomputers and some applications software packages. He did a good job in helping the staff to use these packages.

Case Study (cont’)

• Later, Peter started to develop a billing system for processing sates orders, recording the sales, updating the customer accounts and printing monthly bills. After several months of work on his own. Peter finished the whole program for the system.

Case Study (cont’)

• The clerks of the company slopped using the old manual system and started using Peter's system but encountered immediate difficulties. They complained that the system's operating procedure was too different from the original working procedure and even complicated the tasks. Peter helped the clerks and finally the billing statements were printed. A week later, the company received complaints from some customers saying that their statements were wrong. The company had to redo the erroneous statements manually.

Question (a) ~ 2 marks

• What is the advantage of creating a system over purchasing one from the market?

Question (b) ~ 4 marks

• The fact that Peter's system has caused difficulties for the staff and created errors in the billing statements is probably due to Peter's negligence in the system development process. Suggest two ways by which Peter can improve his work in the system development process.

Question (c) ~ 2 marks

• Suppose everything had gone well with Peter's system. Give one reason for using Peter's approach to system conversion.

Question (d) ~ 6 marks

• Describe how Peter should carry out the system conversion in each of the following cases and support your answers with reasons:

• • Case 1: The manager of the company will not allow any

increase in the error rate of the system during system conversion.

• Case 2: The company has many branches and the system is to be used in each branch.

Techniques, Tools and System documentation

• System flowchart • Data flow analysis (Data flow diagram)• Critical path analysis (PERT charts)• Data dictionary• Decision table• Decision tree

System flowchart (Symbols)Directional flow

Processing

Display Output

Document

System flowchart (Symbol 2)

Manual Input

File storage

2000-AL-COMP STUD 2-8

• The purchasing department of the Gold Light Company is responsible for supplier selection and the issuing of purchase orders.

2000-AL-COMP STUD 2-8 (Cont’)

• In the supplier selection process.– Requirements for items to be ordered and quotations

from the suppliers are obtained from two files;– Tentative orders will be generated after suppliers are

selected;– An orders summary report will also be printed

2000-AL-COMP STUD 2-8 (Cont’)

• In the purchase order issuing process,– The tentative orders will be checked by the

purchasing supervisor via a visual display unit;– Purchase orders will be printed for confirmed orders;– Unconfirmed orders will undergo the supplier

selection process again to select another supplier

2000-AL-COMP STUD 2-8 (Cont’)Supplier

Quotations

TentativeOrders

SupplierSelection

Issue OrderKeyboard

OrderConfirmation

OrdersSummary

Report

2000-AL-COMP STUD 2-8 (Cont’)Supplier

Quotations

TentativeOrders

SupplierSelection

Issue OrderKeyboard

OrderConfirmation

OrdersSummary

ReportUnconfirmed

Orders

Ordersrequirement

PurchaseOrders

Data flow diagram

• Data drive business activities• For example, new sales order data• Simple notations can be easily understood by us

er and business persons

NotationsYourdon Gane and Sarson

Data Flow

Process

Entity(People, organization)

Data Store

Library system(Context diagram)

0

Library system

D1 Book Information

Borrower

Personal Information

BookDetails

Borrowinginformation

D2 Borrowing Records

Errors

All data flows must either originate or terminate at a process

Data flow should not split into two or more different data

flows

Processes need to have at least one input data.