Computer Studies
Systems Development
Systems Development
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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
computerize 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:
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• 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
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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
Supplier
Selection
Order
Confirmation
Keyboard
Tentative
Orders
Issue Order
Orders
Summary
Report
2000-AL-COMP STUD 2-8 (Cont’)
Orders
requirement
Unconfirmed
Orders
Order
Confirmation
Keyboard
Supplier
Quotations
Supplier
Selection
Orders
Summary
Report
Tentative
Orders
Issue Order
Purchase
Orders
Data flow diagram
• Data drive business activities
• For example, new sales order data
• Simple notations can be easily understood by
user and business persons
Notations
Yourdon
Data Flow
Process
Entity
(People, organization)
Data Store
Gane and Sarson
Library system(Context diagram)
D2
Borrowing Records
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Personal
Information
Borrower
Library
system
Book
Details
D1
Book Information
Borrowing
information
Errors
Data flow should not
split into two or more
different data flows
All data flows must either Processes need to have at
least one input data.
originate or terminate at a
process