The if statement
- If statement is used to evaluate something in a program. It is something like making a decision where you have a condition where if it is met do something out of that condition otherwise (if there are no other condition to consider) do something if the condition is not met.
Forms of if statement:
1.) Simple form
Syntax:
if(relational expression)
{
// Block of statement here
//what will the program do
}
else
{
//Block of statement here
//what will the program do
}
Note: else is an option
2.) Compound form
Syntax:
if(relational expression)
{
// Block of statement here
//what will the program do
}
else if(relational expression)
{
//Block of statement here
//what will the program do
}
....
....
....
else if(relational expression)
{
//Block of statement here
//what will the program do
}
else
{
//Block of statement here
//what will the program do
}
3.) Complex form (Nested)
Syntax:
if(relational expression)
{
// Block of statement here
//what will the program do
}
else if(relational expression)
{
//Nested if statement where there is another if statement within
if(relational expression)
{
//Block of statement here
//what will the program do
}
else
{
//Block of statement here
//what will the program do
}
}
else
{
//Block of statement here
//what will the program do
}
Relational Operators:
Operator Description Sample relational expression
> Greater than x > y
< Lesser than Balance < 1000
>= Greater than or equal to Average >=75
<= Lesser than or equal to a <= b
= = Is equal to choice == ‘x’
!= Not equal to answer != ‘d’
Note: There is no space between the 2 equal sign in the (equal to) operator
Expression is any valid combination values, variable, operators, functions, etc.
Sample program:
This program will ask the user to enter his/her age. The program will then evaluate if the age entered is juvenile or not (below 18).
#include<iostream>
using namespace std;
using namespace std;
main( )
{
int age;
cout<<”Enter your age: “;
cin>>age;
if(age<18)
{
cout<”You are an underage”;
}
else
{
cout<<”Welcome to Adulthood!”;
}
return 0;
}
Here the age entered by the user were evaluated if it is lesser than 18 and then execute the block of statement that follows (statement enclose by { and } ). If the evaluation of the condition is not true (false) then the else statement will be executed. Thus, what follows is an example of an output of the program:
Enter your age: 19
Welcome to Adulthood!
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