// Program con6.cpp
#include 
void main()
{
 int age;
 cout << “\n Enter your age : ”;
 cin >> age;
 
 if (age <=5)
 cout << “\n You are a lovely kid.”;
 else
 if (age <= 10)
 cout << “\n You are grwoing up.”;
 else
 if (age <= 20)
 cout << “\n You have not yet grown up.”;
 else 
 if (age <= 30)
 cout << “\n Now you have grown up.”;
 else
 cout << “\n You are a nice gentleman.”;
}

// Program con7.cpp
#include 
void main()
{
 int age;
 cout << “\n Enter your age : ”;
 cin >> age;
 
 if (age <=5)
cout << “\n You are a lovely kid.”;
else
if (age <= 10)
cout << “\n You are growing up.”;
else
if (age <= 20)
cout << “\n You have not yet grown up.”;
else 
if (age <= 30)
cout << “\n Now you have grown up.”;
else
cout << “\n You are a nice gentleman.”;
}

// Program con8.cpp 
#include 
void main()
{
 int age;
 cout << “\n Enter your age : ”;
 cin >> age;
 
 if (age <=5)
 cout << “You are a lovely kid.”;
 else if (age <= 10)
 cout << “You are grwoing up.”;
 else if (age <= 20)
 cout << “You have not yet grown up.”;
 else if (age <= 30)
 cout << “Now you have grown up.”;
 else
 cout << “You are a nice gentleman.”;
}

C++ provides three logical operators as shown in Figure 3

Figure 3

The first two operators, && and ||, are used to combine two conditions in one condition. The third operator,!, negates, or reverse the truth-value of the expression following it. The precedence of logical operators is lower than the relational operators.

Logical  AND Operator: &&

The logical AND operator (&&) is used to combine two expressions into one. If the result of both expressions are true then the result of complete resulting expression is true. If either or both are false then resulting expression would be false.

In program con7.cpp, we have used nested if–elses you have to very careful to match the corresponding ifs and elses. This limitation is overcome by the logical AND operator as:

// Program con9.cpp
#include 
void main()
{
 int age;
 cout << “\n Enter your age : ”;
 cin >> age;
 
 if (age <=5)
 cout << “\n You are a lovely kid.”;
 if (age >5 && age <= 10)
 cout << “\n You are growing up.”;
 if (age > 10 && age <= 20)
 cout << “\n You have not yet grown up.”;
 if (age > 20 && age <= 30)
 cout << “\n Now you have grown up.”;
 if (age > 30)
 cout << “\n You are a nice gentleman.”;
}

// Program con10.cpp
#include 
void main()
{
 char ch;
 cout << “\n Enter a character (a/b/c) : ”;
 cin >> ch;    
 if (ch == ‘a’ || ch == ‘A’)
 cout << “You have entered either a or A”;
 else  if (ch == ‘b’ || ch == ‘B’)
 cout << “You have entered either b or B”;
 else  if (ch == ‘c’ || ch == ‘C’)
 cout << “You have entered either c or C”;
 else
 cout << “Read your question again.”;
}

// Program con11.cpp
#include 
void main()
{
 int year;
 cout << “\nEnter a year : ”;
 cin >> year;
 
 if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0)
 cout << “Leap year.”;
 else
 cout << “Not a leap year.”;
}

! num == 0 is interpreted as (!num) == 0 instead of ! (num == 0).

 ! (num == 0)

expression1 ? expression2 : expression3

Here if the expression1 is true then the value returned by the conditional expression will be expression2; otherwise the value returned will be expression3.

Let us write a simple program that finds the largest number among two numbers.

// Program con12.cpp
#include 
void main()
{
 int a, b, big;
 cout << “\n Enter two numbers : ”;
 cin >> a >> b;
 
 big = (a > b) ? a : b;
 cout << “Largest number : ” << big;
}

big = (a > b) ? a : b;

if (a>b)
 big = a;
 else
 big = b;

// Program con13.cpp
#include 
void main()
{
 int num;
 cout << “\nEnter a number : ”;
 cin >> num;
 
 (num >= 0 ? cout << “Positive number” : cout << “Negative number.”);
}

// Program con14.cpp
#include 
void main()
{
 int a, b, c, big;
 cout << “\nEnter three numbers : ”;
 cin >> a >> b >> c;

 big = (a>b ? (a>c ? a : c) : (b>c ? b : c));
 cout << “Largest number : ” << big;
}

X == 10    // Comparison
 X = 10        // Assignment

// Program con15.cpp
#include 
void main()
{
 int num;
 cout << “\n Enter a number : ”;
 cin >> num;
 
 if (num == 10)
 cout << “You have entered 10”;
 else
 cout << “You have not entered 10”;

 if (num = 10)
 cout << “\nYou have entered 10”;
 else
 cout << “\nYou have not entered 10”;

}

if(10)

if (num == 10) ;
 cout << “You have entered 10”;

cout << “You have entered 10”;

switch (integer-expression)
 {
 case label1 :
 statement(s);
 case label2 :
 statement(s);
 case label3 :
 statement(s);
 ….

 case labeln :
 statement(s);
 default :
 statement(s);
 }

// Program con16.cpp
#include 
void main()
{
 int n;
 cout << “\nEnter a number : ”;
 cin >> n;

 switch (n)
 {
 case 1:
 cout << “\nYou entered 1.”;
 case 2:
 cout << “\nYou entered 2.”;
 case 3:
 cout << “\nYou entered 3.”;
 case 4:
 cout << “\nYou entered 4.”;
 default :
 cout << “\nYou have not entered 1, 2, 3 or 4.”;
 }
}

// Program con17.cpp
#include 
void main()
{
 int n;
 cout << “\nEnter a number : ”;
 cin >> n;

 switch (n)
 {
 case 1:
 cout << “You entered 1.”;
 break;
 case 2:
 cout << “You entered 2.”;
 break;
 case 3:
 cout << “You entered 3.”;
 break;
 case 4:
 cout << “You entered 4.”;
 break;
 default :
 cout << “You have not entered 1, 2, 3 or 4.”;
 }
}

// Program con18.cpp
#include 
void main()
{
 int n;
 cout << “\n Enter a number : ”;
 cin >> n;

 switch (n)
 {
 case 4:
 cout << “You entered 4.”;
 break;
 case 1:
 cout << “You entered 1.”;
 break;
 case 27:
 cout << “You entered 27.”;
 break;
 case 6:
 cout << “You entered 6.”;
 break;
 default :
 cout << “Pardon me.”;
 }
}

// Program con19.cpp
#include 
void main()
{
 char ch;
 cout << “\nEnter any vowel : ”;
 cin >> ch;

 switch (ch)
 {
 case ‘a’:
 cout << “You entered a.”;
 break;
 case ‘e’:
 cout << “You entered e.”;
 break;
 case ‘i’:
 cout << “You entered i.”;
 break;
 case ‘o’:
 cout << “You entered o.”;
 break;
 case ‘u’:
 cout << “You entered u.”;
 break;
 default :
 cout << “You have not entered any vowel.”;
 }
}

// Program con20.cpp
#include 
void main()
{
 char ch;
 cout << “\n Enter any vowel : ”;
 cin >> ch;

 switch (ch)
 {
 case ‘a’:
 cout << “You entered a.”;
 break;
 case 101:
 cout << “You entered e.”;
 break;
 case ‘i’:
 cout << “You entered i.”;
 break;
 case 111:
 cout << “You entered o.”;
 break;
 case ‘u’:
 cout << “You entered u.”;
 break;
 default :
 cout << “You have not entered any vowel.”;
 }
}

// Program con21.cpp 
#include 
void main ()
{
char ch;
cout  <<  “\nEnter any of first four alphabet:”;
cin  >> ch;
switch (ch)
{
case ‘a’:
case ‘A’:
 cout << “You entered a and A”;
 break;            
case ‘b’:
case ‘B’:
cout << “You entered b and B”;
break;
case ‘c’:
case ‘C’:
cout << “You entered c and C”;
break;
case ‘d’:
case ‘D’:
cout << “You entered d and D”;
break;
default:
cout << “You have not entered any of the first four alphabet.”;
}
}

if (num >100 && num <=200)
// statements
else if (num >200 && num <=500)
// statements
else 
// statements

// Program con22.cpp 
#include 
void main()
{
 int number;
 start :
 cout << “\nEnter a number :”;
 cin >> number;
 if (number >=0)
 {
 cout << “Positive number”;
 goto start;
 }
 else
 cout << “You have entered a negative number”;
}

Loops

The statements in programs, which we have seen so far, include either a sequential or decision control structure in which statements are executed exactly once. But in a general programming environment we need to perform an activity over and over, after with a little variation.

C++ provides loops that cause a part of your program to be repeated either a certain number of times or until a specific event occurs. This repetition process continues till a condition is true. When the condition becomes false, the loop terminates and controls transfers to the statement following the loop.

C++ provides three types of loop control structures: the while loop, the do-while loop and the for loop.

The while loop

Before the discussion of a while loop, let us see a program that finds the sum of a five-digit number.

// Program con23.cpp
 #include 
 #include     // header file for abs()–function 
 void main()
 {
 int a, b, c, d, e, sum, number, n;
 cout << “\nEnter a number – “;
 cin >> number;
 n = abs(number);
 a = n%10;
 n = n/10;
 b = n%10;
 n = n/10;
 c = n%10;
 n = n/10;
 d = n%10;
 n = n/10;
 e = n%10;
 sum = a+b+c+d+e;
 cout << “\nSum of digits = ” << sum;
 }

n % 10 and
 n / 10

If you have a 4 digit number then these two steps are repeated for four times, three digit number three times and so on. Whatever may the number of digits of a number, the condition is that repeat these two statements until ‘n’ become 0. Thus it depends upon the number of digits of a number. It may be of any reasonable length using the while loop, we reformulate it so that it can becomes – generalized solution for any number.

The syntax of a while loop is:

 while (test-condition)
 {
 statement(s);
 }

Figure 4illustrates the operation of the while loop.

From this figure it is clear that you must do something within the loop body in order to terminate the loop eventually.

Now let us rewrite the program con23.cpp to make it a generalize solution for any number of any digits.

// Program con24.cpp
#include 
#include 
void main ()
{
int a, sum=0, n , num ;
cout << “\nEnter any number:”;
n = abs(num);
cin >>num;
while (num != 0)
{
a= num  % 10;
 num = num /10;
 sum = sum + a;
}
cout << “ \n Sum of digit =” <}

// Program con25.cpp
#include
void main()
{
int num;
cout<< “\nEnter a positive number: “;
cin>>num;
while (num>=0)
{
 cout<< “Square of  “< cout<< “\nEnter the another positive”;
 cin>>num;
}
 cout<< “\n you have entered a negative number”;
}

// Program con26.cpp
#include
void main()
{
int num;
num=1;
while (num>=0)
{
 cout<< “\n Square of ”< cout<< “\n Enter the another positive”;
}
 cout<< “\n you have entered a negative number”;
}

while (num>=0);

while (num>=0)                                     
 {                             
 }

while (x==0)
 cin>>x;

// Program con27.cpp
#include 
void main()
{
int count; 
float a, b, c, average;
count=1;
while (count<=5)
{
cout<< “\n Enter three numbers :”;
 cin >> a>>b>>c;
 average = (a + b + c)/3.0;
cout<< “Average = ”<< average;
count++;
}    
}

num = 0.2;

num = num +0.5;

do
{
statement(s);

} while(test-condition);

// Program con28.cpp 
#include
 void main()
 {
 int x=0;
while (x==1)
{
cout<< “ \n You have done a big mistake “;
cout<< “\n Never try this again “;
 }
 cout<< “\n  I was a big stupid “;
 }

// Program con29.cpp 
#include
void main()
{
 int x=0;
 do
 {
 cout<< “\n Thanks god”;
 cout<< “\n I have not done a big mistakes”;
 } while (x==1);
cout<< “\n I am a big stupid”;
}

for (initialize_counter; test-condition; update_counter)
{
 statement(s);
}

// Program con30.cpp
#include 
void main()
{
 int n;
 for (n=1; n<=5; n++)
 cout<< “\n N=”<}

// Program con31.cpp
#include 
void main()
{
 int n;
 for (n=10; n>=1; n--)
 cout<< “\nN=”<}

// Program con32.cpp
#include 
void main()
{
 int n;
 for (n=1; n<=5; n++)
 {
cout<< “\n N=”< cout << “\tN*N=”< cout<< “\tN*N*N=”< }
}

for (int n=1;n<=5; n++)
{
 //
}

for (i=1, j=5; i<=5; i++, j--)
 cout<< i <<  “ ” << j << “\n”;

for(n=1;n<=5;)
 {
 statement(s);
n++; }

n=1;
 for( ; n<=5;n++)
 {    
statement(s);
 }

n=1;
 for(;n<=5;)
 {
statement(s);
 n++;
 }

// Program con33.cpp
#include
void main( )
{
 int n;
 for( n=1; n<=20; n=n+3)
cout<< “\nN =”<}

Sum = x – x3/3! + x5/5! – x7/7! + ……… (-1)n-1 x2n-1/(2n-1)!

// Program con34.cpp
# include 
void main ()
{
int i , n ;
 float x, sum , num , den , sn = -1;  
 cout << “\nEnter x and n: ”;
 cin >> x >> n;
 sum = x;
 num = x;
 den = 1;
 for (i=1 ;i <=n-1 ; i ++)  
 {
 num = num * x * x;
 den = den * (2*i) * (2*i+1);
 sum = sum + (num /den ) *sn;
 sn =-sn;
 }
 cout << “\nX=” <}

ith item = (-1)i-1x2i-1 /(2i-1)!(i +1) 
item = (-1)I x(2i+1)/(2i+1)!

// Program con35.cpp
#include
void main ( )
{
 int  i, j, temp; 
 for (i=1;i<=3;i++ ) 
 {
 for ( j=1 ;j<=3 ; j++)
 {
 temp = i * j;    
cout << “\nI=”<< i << “\tJ=”< }
 }
}

 break; 

statement; 
 while (test-condition1)
 {
 statement(s);
 if(test-condition 2)
 break;
 statement(s);
}
statement;

// Program con36.cpp
#include
void main( )
{
 int num , i , flag;
 cout<< “\nEnter a number :”;
 cin>>num;
 i=2;
 flag=0;
 while (i<=num/2)
 {
 if(num%i==0)
 {
 flag = 1;
 break;
 }
 i++;
 }
 if (flag==0)
 cout<< “Prime number: ”<< num;
else
 cout<< “Not a prime number: ” << num;
}

// Program con37.cpp
# include
void main()
{
 int i ,j , k;
 for (i=1;i<=3;i++)
 {
 for(j=1;j<=3; j++)    
 {
 for(  k=1; k<=3;k++)
 {
 if ((i ==j)||(j==k)||(k==i))
 break;
 else
 cout< }
 }
 }
}

continue;

statement; 
 while (test-condition1)
 {
statement (s);        
 if( test-condition 2)
 continue ;
 statement (s);        
}    
statement (s);

// Program con38.cpp
#include 
void main()
{
int i , j , k ;
 for ( i=1; i<=3; i++)
 {
 for ( j=1 ;j<=3;j++)
 {
 for (k=1 ;k<=3;k++)
 {
 if ((i==j)||(j==k)||(k==i))
 continue ;
 else
 cout << "\n" << i << "\t" << j << "\t" << k ;
 }
 }
 }
}

C++ provides two types of decision making statements: if-else statement and switch-case statement. The conditional operator ? and : can often be used in place of a simple if – else statement. Relational operators compare two numbers and its result is either true or false. A true is indicated by a non-zero value and false by 0.

The logical AND and OR operators combine two or more boolean expressions into one. The logical NOT operator changes  the boolean value from true or false, or from false to true. The break statement terminates the switch statement and than the control to the statement, if any following the switch statement. The goto statement transfers the control to the label.

A loop executes the same statement or a set of statements over and over as long as the loop test-condition is true and the loop terminates when the test-condition becomes false.  C++ provides three types of the loop – the while loop, the do-while loop and the for loop. The while loop and for loop are entry-controlled loops, that is they examine the test-condition prior to the execution of the loop body. The do-while loop is an exit-condition loop, that is it examines the test-condition after executing the loop body. A loop body may consist of a single statement, or a block of multiple statements enclosed within pair of braces.

The break statement terminates the loop in which it is placed and transfers the control to the first statement following that loop. The continue statement skips the remaining statements of the loop and transfers the control to the top of the loop in which it is placed.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~END~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~