If Else Switch Case in C++ Programming

If..Else and Swicth..Case construct in C++ Programming

When we have multiple conditions to check and act accordingly, we can use If..Else or Switch..Case.

/*Following Program Displays Corresponding Day Name. 1 prints Sunday, 2 Prints Monday and so on…. */

  Line 1.           #include<iostream.h>

  Line 2.           void main()

  Line 3.           {

  Line 4.           int a;

  Line 5.           cout<<”Enter A Number between 1 to 7 ”;

  Line 6.           cin>>a;

  Line 7.           if(a==1)

  Line 8.           {

  Line 9.           cout<<”Sunday”;

  Line 10.      }

  Line 11.      if(a==2)

  Line 12.      {

  Line 13.      cout<<”Monday”;

  Line 14.      }

  Line 15.      if(a==3)

  Line 16.      {

  Line 17.      cout<<”Tuesday”;

  Line 18.      }

  Line 19.      if(a==4)

  Line 20.      {

  Line 21.      cout<<”Wednesday”;

  Line 22.      }

  Line 23.      if(a==5)

  Line 24.      {

  Line 25.      cout<<”Thursday”;

  Line 26.      }

  Line 27.      if(a==6)

  Line 28.      {

  Line 29.      cout<<”Friday”;

  Line 30.      }

  Line 31.      if(a==7)

  Line 32.      {

  Line 33.      cout<<”Saturday”;

  Line 34.      }

  Line 35.      else

  Line 36.      {

  Line 37.      cout<<”Sorry !!! Wrong Input.”;

  Line 38.      }

  Line 39.      }

Now we can get the same result from the following program using switch..case

/*Following Program Displays Corresponding Day Name. 1 prints Sunday, 2 Prints Monday and so on…. */

  Line 1.           #include<iostream.h>

  Line 2.           void main()

  Line 3.           {

  Line 4.           int a;

  Line 5.           cout<<”Enter A Number between 1 to 7 ”;

  Line 6.           cin>>a;

  Line 7.           switch(a)

  Line 8.           {

  Line 9.           case 1: cout<<”Sunday”;

  Line 10.      case 2: cout<<”Monday”;

  Line 11.      case 3:cout<<”Tuesday”;

  Line 12.      case 4:cout<<”Wednesday”;

  Line 13.      case 5:cout<<”Thursday”;

  Line 14.      case 6:cout<<”Friday”;

  Line 15.      case 7:cout<<”Saturday”;

  Line 16.      default: cout<<”Sorry !!! Wrong Input.”;

  Line 17.      }

  Line 18.      }

In Switch Case, default does the work as of else part in an If…Else construct.   Now if we run the above program we get some unexpected results. If we enter the value of a as 2. We get Monday, Tuesday, Wednesday….Sorry Wrong Input.

Why because in switch case, there is a behavior called “FALL THROUGH” which means when a matching case is found, it automatically reaches all the cases defined below the matched case till we get break or end of switch. So we need to modify the above code to get desired results:

  Line 1.           #include<iostream.h>

  Line 2.           void main()

  Line 3.           {

  Line 4.           int a;

  Line 5.           cout<<”Enter A Number between 1 to 7 ”;

  Line 6.           cin>>a;

  Line 7.           switch(a)

  Line 8.           {

  Line 9.           case 1: cout<<”Sunday”; break;

  Line 10.      case 2: cout<<”Monday”; break;

  Line 11.      case 3:cout<<”Tuesday”; break;

  Line 12.      case 4:cout<<”Wednesday”; break;

  Line 13.      case 5:cout<<”Thursday”; break;

  Line 14.      case 6:cout<<”Friday”; break;

  Line 15.      case 7:cout<<”Saturday”; break;

  Line 16.      default: cout<<”Sorry !!! Wrong Input.”;

  Line 17.      }

  Line 18.      }