Decision making in C++

1. Control statement:

• All the instructions are executed sequentially by default when no repetitions of some calculations are necessary.
• In some situation, we may have to change the execution order of statements based on condition or to repeat a set of the statement until certain conditions are met.

Tyes:

1. If statement
2. If – else statement
3. Nested if....else statement
4. If ....else ladder
5. Switch case

1. If statement:

It is used to check the condition and if true the condition then it executes.

Syntax:

 if (condition)

{

          True statement;

}

Example program for if:

#include<iostream.h>

#include<conio.h>

void main()

{

int a;

clrscr();

cout<<"\n Enter a value:");

cin>>a;

if (a>=5)

    {

          cout<<"\n The entered number "<<a<<" is greater than 5";

     }

getch();

}

Output:

if condition:

False case:

2. If – else statement:

It is used to check both conditions i.e. true and false.

It executes only one condition at a time.

Syntax:

if (condition)

    {

          True statement

     }

else

    {

          false statement;

     }

Example program for if-else:

#include<iostream.h>

#include<conio.h>

void main()

{

int a;

clrscr();

cout<<"\n Enter a value:");

cin>>a;

if (a>5)

      {

   cout<<"\n The entered number "<<a<<" is greater than 5";

       }

else

      {

  cout<<"\n The entered number "<<b<<" is less than 5";

      }

getch();

}

Output:

if condition:

else condition:

3. Nested if....else statement:

Multiple if-else conditions are validating i.e. within condition check first after that execute.

Syntax:

if(condition 1)

   {

          if(condition 2)

              {

                   True statement2;

               }

          else

              {

                   False statement2;

               }

   }

else

    {

          False statement1;

     }

Example program for nested if...else:

#include<iostream.h>

#include<conio.h>

void main()

{

int  a,b;

clrscr();

cout<<"\n Enter a result:\n 1.pass\n 2.fail\n press 1 or 2\n");

cin>>a;

if (a==1)

     {

 cout<<"\n Enter total mark:");

cin>>b;

if(b>450)

   {

cout<<"\n You can get first group i.e. maths group");

    }

else

   {

cout<<"\n You can get all group except the first group");

   }

      }

else

    {

cout<<"\n Passed student only can join the 11th standard");

     }

getch();

}

Output:

if-if condition

if-if-else case:

else condition:

4. The if...else ladder:

It is similar to nested if but it checks continually.

Syntax:

if(condition)

   {

          Statement1;

    }

else if(condition 2)

   {

          Statement2;

    }

else if(condition 3)

   {

          Statement3;

    }

else

   {

          Statement4;

   }

Example program for if...else ladder:

#include<iostream.h>

#include<conio.h>

void main()

{

int  a,b,c;

clrscr();

cout<<"\n Enter 3 values: ");

cin>>a>>b>>c;

if( (a>b) &&(a>c))

  {

cout<<"\n Biggest value "<<a<<" is a";

  }

else if(b>c)

  {

cout<<"\n Biggest value "<<b<<" is b";

   }

else

  {

cout<<"\n Biggest value "<<c<<"  is c";

   }

     getch();

}

Output:

if condition:

else if  condition:

else condition:

5. Switch case:

It is used to execute a particular group of a statement .

Syntax:

 switch(expression)

  {

          case condition 1:

          statement1;

          break;

          case condition 2:

          statement2;

          break;

          .........

          .........

          default

          statements

          break;

  }

Example program for switch case:

#include<iostream.h>

#include<conio.h>

void main()

{

int  choice;

clrscr();

cout<<"\n Enter a choice 1 or 2";

cin>>choice;

switch(choice)

  {

case 1:

cout<<"\n You are chooses option 1 ";

break;

case 2:

cout<<"\n You are chooses option 2 ";

break;

default:

cout<<"\n You can only entered 1 or 2 choice ";

break;

  }

getch();

}

Output:

Case 1:

Case 2:

Default case:

2. Branching and looping:

It is used to execute continually until the condition becomes false.

Types:

• While
• Do while
• For

1. While:

It first checks the condition then executes the result until becomes false.

Syntax:

 while (condition)

{

          Statements;

}

Example program for while condition:

#include<iostream.h>

#include<conio.h>

void main()

{

int  i=1,sum=0;

clrscr();

while(i<=5)

      {

sum=sum+i;

i++;

      }

cout<<"\n The sum of numbers upto 5 is : "<<sum;

getch();

}

Output:

2. do while:

It is first to perform some operation after that check the conditions.

It's opposite to the while condition.

Syntax:

do

{

          Statements;

}

while (condition);

Example program for do while condition:

#include<iostream.h>

#include<conio.h>

void main()

{

int  i=1,sum=0;

clrscr();

do

  {

sum=sum+i;

i++;

  }

while(i<=5);

cout<<"\n The sum of numbers upto 5 is : "<<sum;

getch();

}

Output:

3. for loop:

It is used to execute a set of instructions repeatedly until the condition becomes false.

Syntax:

 for(initialization ;condition ;increment or decrement)

{

          Statement;

}

Example program for for loop:

#include<iostream.h>

#include<conio.h>

void main()

{

int  i;

clrscr();

for(i=1;i<=10;i++)

    {

cout<<i<<endl;

     }

getch();

}

Output:

Share: