08 Decision Making

Hello in this post we will know more about Decision Making so let’s get started 🙂

Decision making structures require that the programmer specify one or more conditions to be evaluated or tested by the program, along with a statement or statements to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

Following is the general from of a typical decision making structure found in most of the programming languages:
Decision making

 

C# provides following types of decision making statements:

  • if statement.
  • if .. else statement.
  • nested if statements.
  • switch statement.
  • nested switch statements.

If statement: An if statement consists of a boolean expression followed by one or more statements.
Syntax:

if (boolean_expression)
{
 /* statement(s) will execute if the boolean expression is true */ 
}

If the boolean expression evaluates to true, then the block of code inside the if statement will be executed. If boolean expression evaluates to false then the first set of code after the end of the if statement (after the closing curly brace) will be executed.

If…else statement: An if statement can be followed by an optional else statement, which executes when the boolean expression is false.
Syntax:

if (boolean_expression)
{
 /* statement(s) will execute if the boolean expression is true */ 
}
else
{
/* statement(s) will execute if the boolean expression is false */ 
}

If the boolean expression evaluates to true, then the if block of code will be executed otherwise else block of code will be executed.

 

The if…else if…else Statement: An if statement can be followed by an optional else if…else statement, which is very useful to test various conditions using single if…else if statement.
When using if , else if , else statements there are few points to keep in mind.

  • An if can have zero or one else’s and it must come after any else if’s.
  • An if can have zero to many else if’s and they must come before the else.
  • Once an else if succeeds, none of the remaining else if’s or else’s will be tested.

Syntax:

if (boolean_expression 1)
{
 /* statement(s) will execute if the boolean expression 1 is true */ 
}
else if (boolean_expression 2)
{
/* statement(s) will execute if the boolean expression 2 is true */ 
}
else if (boolean_expression 3)
{
/*statement(s) will execute if the boolean expression 3 is true */
}
else
{
/* executes when the none of the above condition is true */ 
}</pre>
<pre>

 

nested if statements: It is always legal in C# to nest if-else statements, which means you can use one if or else if statement inside another if or else if statement(s).
Syntax:

if (boolean_expression 1)
{
 /* Executes when the boolean expression 1 is true */ 
 if (boolean_expression 2)
 {
  /* Executes when the boolean expression 2 is true */ 
 }
}

 

You can nest else if…else in the similar way as you have nested if statement.

switch statement: A switch statement allows a variable to be tested for equality against a list of values. Each value is called a case, and the variable being switched on is checked for each switch case.
Syntax:

switch(expression)
{
     case constant-expression  :
        statement(s);
        break; /* optional */
     case constant-expression  :
        statement(s);
        break; /* optional */
        /* you can have any number of case statements */
     default : /* Optional */
        statement(s);
 } 

The following rules apply to a switch statement:

  • The expression used in a switch statement must have an integral or enumerated type, or be of a class type in which the class has a single conversion function to an integral or enumerated type.
  • You can have any number of case statements within a switch. Each case is followed by the value to be compared to and a colon.
  • The constant-expression for a case must be the same data type as the variable in the switch, and it must be a constant or a literal
  • When the variable being switched on is equal to a case, the statements following that case will execute until a break statement is reached.
  • When a break statement is reached, the switch terminates, and the flow of control jumps to the next line following the switch statement
  • Not every case needs to contain a break. If no break appears, the flow of control will fall throught subsequent cases until a break is reached.
  • A switch statement can have an optional default case, which must appear at the end of the switch. The default case can be used for performing a task when none of the cases is true. No break is needed in the default case.

 

nested switch statement: It is possible to have a switch as part of the statement sequence of an outer switch. Even if the case constants of the inner and outer switch contain common values, no conflicts will arise.
Syntax: 

switch(ch1)
  {
    case 'A':
        printf("This A is part of outer switch" );
       switch(ch2)
        {
          case 'A':
             printf("This A is part of inner switch" );
             break;
          case 'B': /* inner B case code */
       }
       break;
    case 'B': /* outer B case code */
 }

and now we have covered all the statements of Decision Making which was our topic in this post so, now i have prepared an Exaple for all of these statements. :)and here’s the link: http://1drv.ms/QljU81

Thanks for your time 🙂
Hope that was useful and don’t forget to feel free to contact me 🙂

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