BRANCHING STATEMENTS

Conditional statements 

These statements can be used to change the flow of program after making some decision or condition.

Basically these are again sub categorized into four types as follows

1. If statement

2. If…..else Statement

3. Nested if statement

4. Switch - case statement

If Statement :

This is a conditional statement used in C to check condition or to control the flow of execution of statements. This is also called as 'decision making statement or control statement.' The execution of a whole program is done in one direction only.

 Syntax:
 
if(condition)
{
     statements;
}

  

In above syntax, the condition is checked first. If it is true, then the program control flow goes inside the braces and executes the block of statements associated with it. If it returns false, then program skips the braces. If there are more than 1 (one) statements in if statement then use { } braces else it is not necessary to use.

Program :

 /*  Program to demonstrate if statement.
#include <stdio.h>

#include <conio.h>

void main()

{

     int a;

     a=5;

     clrscr();

     if(a>4)

         printf("\nValue of A is greater than 4 !");

     if(a==4)

         printf("\n\n Value of A is 4 !");

     getch();

}

Output :

Value of A is greater than 4 !_ 4 !_

If-Else Statement :

 

This is also one of the most useful conditional statement used in C to check conditions.

Syntax:

if(condition)

{

     true statements;

}

else

{

     false statements;

}

In above syntax, the condition is checked first. If it is true, then the program control flow goes inside the braces and executes the block of statements associated with it. If it returns false, then it executes the else part of a program.
 

/*  Program to demonstrate if-else statement.

#include <stdio.h>

#include <conio.h>

void main()

{

     int no;

     clrscr();

     printf("\n Enter Number :");

     scanf("%d",&no);

     if(no%2==0)

         printf("\n\n Number is even !");

     else

                            printf("\n\n Number is odd !");

                            getch();

                          }

Output :

 

En Enter Number :11

 N Number is odd

Nested If-Else Statement :

It is a conditional statement which is used when we want to check more than 1 conditions at a time in a same program. The conditions are executed from top to bottom checking each condition whether it meets the conditional criteria or not. If it found the condition is true then it executes the block of associated statements of true part else it goes to next condition to execute.

Syntax:

if(condition)

{

Statements…..

     if(condition)

     {

         statements;

     }

     else

     {

         statements;

     }

}

else

{

Statements…..

     if(condition)

     {

         statements;

     }

     else

     {

         statements;

     }

}

In above syntax, the condition is checked first. If it is true, then the program control flow goes inside the braces and again checks the next condition. If it is true then it executes the block of statements associated with it else executes else part.

Program :

/*  Program to demonstrate nested if-else statement

#include <stdio.h>

#include <conio.h>

void main()

{

     int no;

     clrscr();

     printf("\n Enter Number :");

     scanf("%d",&no);

     if(no>0)

     {

         printf("\n\n Number is greater than 0 !");

     }

     else

     {

         if(no==0)

         {

              printf("\n\n It is 0 !");

         }

         else

         {

              printf("Number is less than 0 !");

         }

     }

     getch();

}

Output :

Enter Number : 0

It is 0 !_

If..else if Statement
If else if structure is the other way of representing an if..else …if structure. i.e instead of using if statement again in the else part of the if …else structure we can use a single statement as “else if”. This statement works exactly the same as if..else if structure.

Syntax:  

If(condition)

{ statement to be done;

}

Else if(condition)

{

Statetements…….

}

Switch case Statement :

This is a multiple or multiway branching decision making statement.

When we use nested if-else statement to check more than 1 conditions then the complexity of a program increases in case of a lot of conditions. Thus, the program is difficult to read and maintain. So to overcome this problem, C provides 'switch case'.

Switch case checks the value of a expression against a case values, if condition matches the case values then the control is transferred to that point.

Syntax:
 
switch(expression)
{
     case expr1:
         statements;
             break;
     case expr2:
         statements;
        break;   case exprn:
         statements;
             break;                           
   default:
         statements;
}

In above syntax, switch, case, break are keywords.

 expr1, expr2 are known as 'case labels.'

Statements inside case expression need not to be closed in braces.

Break statement causes an exit from switch statement.

Default case is optional case. When neither any match found, it executes.

Program :

/*  Program to demonstrate switch case statement.

#include <stdio.h>

#include <conio.h>

void main()

{

     int no;

     clrscr();

     printf("\n Enter any number from 1 to 3 :");

     scanf("%d",&no);

     switch(no)

     {

         case 1:

              printf("\n\n It is 1 !");

              break;

         case 2:

              printf("\n\n It is 2 !");

              break;

         case 3:

              printf("\n\n It is 3 !");

              break;

         default:

              printf("\n\n Invalid number !");

     }

     getch();

}

Output 1 :

Enter any number from 1 to 3 : 3

It is 3 !_

RULES FOR DECLARING SWITCH CASE :

·         The case label should be integer or character constant.

·         Each compound statement of a switch case should contain break statement to exit from case.

·         Case labels must end with (:) colon.

ADVANTAGES OF SWITCH CASE :

·         Easy to use.

·         Easy to find out errors.

·         Debugging is made easy in switch case.