use of if and switch statement in c++

Flow Of Control

if statement

syntax of the if statement

if (condition)
{
  statement(s);
}

From the flowchart it is clear that if the if condition is true, statement is executed; otherwise it is skipped. The statement may either be a single or compound statement.

if else statement

syntax of the if - else statement

if (condition) 
  statement1; 
else 
  statement2;

From the above flowchart it is clear that the given condition is evaluated first. If the condition is true, statement1  is executed. If the condition is false, statement2 is executed. It should be kept in mind that statement and statement2 can be single or compound statement.

if example	if else example
if (x == 100)     cout << "x is 100";	if (x == 100)     cout << "x is 100"; else     cout << "x is not 100";

Nested if statement

The if block may be nested in another if or else block. This is called nesting of if or else block.

syntax of the nested if statement

if(condition 1) 
{ 
  if(condition 2) 
  { 
    statement(s); 
  } 
}

if(condition 1) 
  statement 1; 
else if (condition 2) 
  statement2; 
else
  statement3;

if-else-if example

if(percentage>=60)      cout<<"Ist division"; else if(percentage>=50)      cout<<"IInd division"; else if(percentage>=40)      cout<<"IIIrd division"; else      cout<<"Fail" ;

switch statement

The if and if-else statements permit two way branching whereas switch statement permits multiple branching. The syntax of switch statement is:

switch (var / expression) 
{ 
   case constant1 : statement 1; 
   break; 
   case constant2 : statement2; 
   break; 
   .
   .
   default: statement3; 
   break; 
}

The execution of switch statement begins with the evaluation of expression. If the value of expression matches with the constant then the statements following this statement execute sequentially till it executes break. The break statement transfers control to the end of the switch statement. If the value of expression does not match with any constant, the statement with default is executed.

Some important points about switch statement

·         The expression of switch statement must be of type integer or character type.

·         The default case need not to be used at last case. It can be placed at any place.

·         The case values need not to be in specific order.