Conditional statements in C language

Conditional statements helps to achieve decision making behavior in programming. While working on software development, it is a common phenomenon that we do specific tasks based on some conditions.

In a real world scenario, like if your age is above 18 then you can vote else you can’t.

In C language, any non-zero are considered as true, and if it is either zero or null, then it is assumed as false value.

C language has following different conditional statements:

  • if
  • if...else
  • if...else if...else (or if-else ladder)
  • ? : (Conditional operator)
  • switch

if statement

Syntax:

if (condition) {
  // statements got executed when condition is true
}

Example:

int age = 15;

if (age < 18) {
  printf("You are yet to meet voting age.")
}

if...else statement

Syntax:

if (condition) {
  // statements got executed when condition is true
} else {
  // statements got executed when condition is false
}

Example:

int age = 20;

if (age > 18) {
  printf("Congratulations! You are ready to vote now.")
else {
  printf("You are yet to meet voting age.")
}

if-else ladder

Sometimes, we need to decided more than two then in such case if-else ladder is used.

Syntax:

if (condition1) {
   // statements got executed when condition1 is true
}
else if(condition2) {
   // statements got executed when condition2 is true
}
else if (condition3) {
   // statements got executed when condition2 is true
}
.
.
else {
   // statements got executed when all above if conditions are false
}

Example:

int age = 20;

if (age < 10) {
  printf("You are still child.")
else if (age >= 10 && age < 18) {
  printf("You are yet to meet voting age.")
else if (age > 18) {
  printf("Congratulations! You are ready to vote now.")
else {
  printf("Invalid age")
}

Conditional or Ternary Operator

The ? : operator is also known as Conditional operator. It is the only one operator which takes three operands and hence also known as Ternary operator. We can use this operator to replace simple if..else statement.

Syntax:

expression 1 ? expression 2 : expression 3

If expression 1 is true then compiler executes expression 2 else expression 3 is executed.

Example:

int age = 10;
age > 18 ? printf("Congratulations! You are ready to vote now.") : printf("You are yet to meet voting age.");

Switch statement

switch statement allows us to choose only one among many given choices. The expression in switch is evaluated to some integral value which is then compared with different cases. Later, the block which the matching case is executed.

Syntax:

switch(expression)
{
  case constant-1:
    block one;
    break;

  case constant-2:
    block two;
    break;

  case constant-3:
    block three;
    break;

  ...

  case constant-N:
    block N;
    break;

  default:
    default-block;
}

Example:

char operator = '+';

switch(operator) {
  case '+':
    printf("Addition operation.\n");
    break;

  case '-':
    printf("Subtraction operation.\n");
    break;

  default:
    printf("Invalid operation.\n");
}

// output
Addition operation.
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