Dec1999 SD206 : Systems Design (Question3)Suggested Solutions

(a)	Flowcharts are often described as being too sequential in nature.List three characteristics of flowcharts which support this argument. One mark should be awarded for each valid point (up to a maximum of three marks). Examples include the following: •Activities are represented from top to bottom and from left to right. •There must be a start point and an end point. •Activities are commonly ordered in a deterministic sequence. Other valid answers should also receive marks .	[3]
(b)	Give two ways in which the design of a system can be disadvantaged if flowcharts are used. One mark should be awarded for each valid point (up to a maximum of two marks). Examples include the following: •Global data might be used. •The logic ofthe design tends to be intertwined,meaning that it is difficult to trace and test. •There is no effective control as a result ofno superior/subordinate relationship. •Flowcharts do not help in partitioning a system design. Other valid answers should also receive marks	[2]
(c)	Illustrate,using examples,each of the following Nassi-Schneiderman chart symbols: (i)Sequence process.[2 marks ] (ii)Condition decision process.[2 marks ] (iii)Case decision process.[2 marks ] (iv)Iteration process.[2 marks ] In each case,one mark should be awarded for getting the structure of the symbol,and a further mark should be awarded for illustrating the symbol with a suitable example.	[8]
(d)	List two drawbacks of using Nassi-Schneiderman charts. One mark should be awarded for each valid point (up to a maximum of two marks). Examples include the following: •Nassi-Schneiderman charts can be difficult to draw,especially ifthere are a large number ofnested ifstatements. •Nassi-Schneiderman charts do not link to a data dictionary. •Nassi-Schneiderman charts cannot be used at a higher level to illustrate the general structure of a program. Other valid answers should also receive credit.	[2]