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Flowcharts
KEY WORD
A flowchart is a graphical representation of a detailed design for an algorithm. It uses a set of symbols, which are illustrated and defined in Table 2.1. Symbol
Use The terminator symbol: there is one at the start and one at the end (referred to as ‘stop’) of the flowchart sequence.
flowchart: a diagram used to document a detailed design for an algorithm that shows the logical flow of the actions.
FT
An action symbol: it is used to show that the action required is either an input of a value or the output of a value. There must be only one arrow going in and one arrow going out.
An action symbol: sometimes referred to as the ‘process symbol’. It is where one or more actions can be defined. There must be only one arrow going in and one arrow going out.
A
An action symbol: referred to as the ‘decision symbol’. It defines a condition to be tested.
There must be only one arrow going in but there must be two arrows coming out.
R
One of the outgoing arrows must be marked TRUE or T and the other marked FALSE or F. The arrow is used to define the sequence or flowline of the actions defined in the flowchart.
Table 2.1: Flowchart symbols
D
There are a couple of points to make about the use of flowcharts: 1
2
A flowchart is normally presented as a design going from top to bottom, rather than from left to right, with the start terminator at the top and the stop terminator at the bottom. A flowchart is normally used for a detailed design. In this case, each of the three action symbols must contain specific details of the action. Pseudocode is suitable for this.
In the following chapters, when a detailed design is provided for you, this will usually be presented as a flowchart and as pseudocode. Flowchart 2.1 shows an example of a flowchart constructed as a preliminary design for a program that provides a quiz for a user. Note how iteration is included by the use of an arrow returning to an earlier stage in the algorithm.
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