Alternative statement:
A condition is a phrase that describes a test of the state. If C is a condition and both S1 and S2 are statements, then
is a statement, called an alternative statement, that describes the following action:
1. Test whether C is true or false.
2. If C is true, then do S1; otherwise do S2.
In pseudo code, the two alternatives S1 and S2 are indicated by indenting them from the keywords if and else, respectively. Alternative control flow is depicted in the flowchart. Condition C has two outgoing arrows, labeled true and false. The true arrow points to the S1 box. The false arrow points to the S2 box. Arrows out of S1 and S2 point to the same box, the box after the alternative statement.
Conditional statement:
Sometimes we need to execute a statement only if a condition is true and do nothing if the condition is false. This is equivalent to the alternative statement in which the else clause is empty. This variant of alternative statement is called a conditional statement.
If C is a condition and S is a statement, then
1. Test whether C is true or false.
2. If C is true then do S; otherwise do nothing.
The conditional control flow is depicted in the flowchart.
