If/else Structure

We have seen that the if structure executes its block of statement(s) only when the condition is true, otherwise the statements are skipped. The if/else structure allows the programmer to specify that a different block of statement(s) is to be executed when the condition is false. The structure of if/else selection is as follows.



Thus using this structure we can write the construct of our program as:



In this construct, the program checks the condition in if statement .If the condition is true, then the line "Amer is greater than Amara" is printed. Otherwise (if condition is not true), the statement related to else is executed and the message "Amer is younger than Amara" is printed. Here in if/else structure an important thing is that the else part is executed for all the cases (conditions) other than the case which is stated in the if condition.
And in the comparison, we know that there are three conditions i.e. first value is greater than the second value, first value is less than the second value and first value is equal to the second value. Here in the above program construct the else part competes the greater than conditions and covers both less than and equal to conditions.
Thus in the above program construct, the message "Amer is younger than Amara" is displayed even if Amer’s age is the same as Amara’s age. This is logically incorrect and so to make this correct, we should display the message "Amer is younger than or is of the same age as Amara". Now this statement describes both the cases other than the one ‘Amer is greater than Amara'.
The use of else saves us from writing different if statements to compare different conditions, in this way it cover the range of checks to complete the comparison.
If we want to state the condition "Amer is greater than or is of the same age as Amara’s" then we use the greater than or equal to operator (i.e. >=) in the if statement and less than operator ( < ) in the else statement to complete the comparison. It is very important to check all the conditions while making decisions for good, complete and logical results. Make sure that all cases are covered and there is no such case in which the program does not respond. The flow chart of our program with if/else structure will be as follow.



For previous lesson click here: IF Sample Program 1
For next lesson click here: Logical Operators

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If/else Structure