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Computer Science Input N or more paths. Once the conditional
Start
execution is finished, it will re-join
before leaving the structure. Selection
control structure uses ‘IF…THEN’
or ‘IF…. THEN ...ELSE’ or a CASE
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structure in pseudocodes and flowcharts.
Input M
IF … THEN
IF…THEN, the structure executes the
Sum = N + M
process if the condition is true. If it is not
true, it skips the process. The diamond-
Output Sum shaped box in flowcharts represents the
decision or condition. The syntax for
END IF…THEN is:
IF (Condition) THEN
Figure 8.8: Example of sequential control
structure Statement

Selection control structure in END IF;
flowcharts The corresponding flowchart is

The selection control structure is used represented as shown in Figure 8.9.
to make decisions on an algorithm.
A condition is a logical expression or
statement that can be assessed as true or YES Condition
false. The ability to control flow of the
algorithm by making decisions based
on conditions is provided by selection
control structures. It enables choosing Statement(s) NO
between several paths of execution.
Examples from real life include deciding
what to wear based on the weather. You
dress in a T-shirt and shorts when it is

sunny, but you take an umbrella and a
raincoat when it is raining. Figure 8.9: Example of IF-THEN selection

Example of IF…THEN selection
Under the selection control structure, control structure
one condition is evaluated first and then
the program flows into one of the two Write an algorithm using a flowchart
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