Flow of control

 A single statement is called a simple statement some examples of simple statements are given below

 int  a = 100;
 s = S + a;
 count ++;

 The compound statement

{
cin>>a>>b;
c=a+b;
cout<<c;
}

Selective execution(conditional statements)

In some cases, it is desired that a selected segment of a program be executed on the basis of a test depending upon the state of a particular condition being true or false in C++' if statement' is used for  selective execution of the program

 The if statement

This statement helps us in the selection of 1 out of two alternative courses of actions the general form of "if statement" is given below

 if (expression)

{

 statement sequence

}

 Where if is a reserved word expression is a Boolean expression enclosed within a set of Parentheses. These Parentheses are necessary even if there is a single variable in the expression statement sequence is either a simple statement or a block. However, it cannot be declaration

Example of acceptable if statements are:

1-if (A>B) A=B;
2-if (total < 100)
   {
   total = total + val;
   count = count+1;
   }

The if-else statement

 It may be observed from the above examples that the simple if statement does nothing when the expression is false an if-else statement takes care of this aspect

 The general form of this construct is given below

 if (expression)
{
 statement sequential
}
 else
{
 statement sequential
}

 where if is a reserved word expression is a Boolean expression returned within parentheses statement sequential can be a simple or a compound statement else is a reserved word statement sequential can be an as simple or compound statement

If (x == 100)

cout<<"Equal to 100";

else

cout<<"\n Not equal to 100";

Example Program:

Write a program that reads a year and determine whether it is a leap year or not.

#include<iostream>
using namespace std;
int main()
{
int leapyear;
cout<<"Enter the year"<<endl;
cin>>leapyear;
if (leapyear % 4 == 0) && (leapyear % 100 != 0) || (leapyear % 400 == 0)
{
cout<< leapyear <<"is a leap year"<<endl;
}
else
{
cout<<leapyear<<" is not leap year"<<endl; 
}