Pascal Programming Today Chapter 4 1 »Conditional statements allow the execution of one of a number of possible operations. »Conditional statements include:

Pascal Programming Today Chapter 4

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» Conditional statements allow the execution of one of a number of possible operations.

» Conditional statements include:–if statements

–case statements


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If-then-else Statements

Syntax of if-then-else statements

if <Condition>

then <Statement A>

else <Statement B>

May be a Boolean constant, Boolean variable or Boolean expression.


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if <Condition>

then <Statement A>

else <Statement B>

Will be executed if <Condition> is TRUE.


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if <Condition>

then <Statement A>

else <Statement B>

Will be executed if <Condition> is FALSE.


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Flowchart of an if-then-else statement


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» Sometimes, more than one statement is required to be executed under the condition.

» In such case, a compound statement should be used.


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» A compound statement consists of two or more simple statements enclosed by a pair of reserved words begin and end.


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Syntax of if-then-else statements with compound statements

if <Condition>

then begin

<Statement A1>;

<Statement AN>

end

else begin

<Statement B1>;

<Statement BN>

end

Compound statement

Compound statement


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Flowchart of an if-then-else statement with compound statements


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If-then Statements

Syntax of if-then statements

if <Condition>

then <Statement>


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Flowchart of an if-then statement


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Syntax of if-then statements with compound statements

if <Condition>

then begin

<Statement 1>;

<Statement 2>;

<Statement N>

end


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Flowchart of an if-then statement with compound statement


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Nested If Statements

» An if statement may be nested by another if statement to form a nested if statement.


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Syntax of nested if statements

if <Condition C1>

then if <Condition C2>

then <Statement A1>

else <Statement A2>

else if <Condition C3>

then <Statement B1>

else <Statement B2>


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Flowchart of a nested if statement


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» Reserved word else should be matched to the nearest preceding if in nested if statements.


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Case Statements

» A case statement is preferred for selection involving more than three alternatives.


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Syntax of case statements

case <Selector> of

<Case label 1> : <Statement 1>;


<Case label N> : <Statement N>

end

A variable or an expression of ordinal data types (integer, char or Boolean).


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case <Selector> of




end

Lists of possible values of <Selector>.


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case <Selector> of




end

Simple or compound statements.


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» Only one selection on the list of statements will be executed.

» No statements will be executed if no case label match the selector.

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Pascal Programming Today Chapter 4 1 »Conditional statements allow the execution of one of a number of possible operations. »Conditional statements include: