Ternary Operator in C: A Compact Conditional Tool

The ternary operator (?:) in C serves as a conditional operator, allowing you to simplify your code by condensing multiple if-else statements into a more concise form. This section explains the syntax and usage of the ternary operator for efficient coding.

Ternary Operator in C

The ternary operator (?:) in C is a type of conditional operator. The term "ternary" implies that the operator has three operands. It's often used to condense multiple conditional (if-else) statements into a more compact form.

Syntax of Ternary Operator in C

The syntax for the ternary operator is:

exp1 ? exp2 : exp3

It uses three operands:

• exp1 - A Boolean expression that evaluates to true or false.
• exp2 - Returned by the operator when exp1 is true.
• exp3 - Returned by the operator when exp1 is false.

Example 1: Ternary Operator in C

This C program uses the ternary operator to check if the value of a variable is even or odd:

#include <stdio.h>

int main() {
   int a = 10;
   
   (a % 2 == 0) ? printf("%d is Even \n", a) : printf("%d is Odd \n", a);

   return 0;
}

Output

10 is Even

Change the value of a to 15 and run the code again. The output will be:

15 is Odd

Example 2

This example rewrites the logic of checking odd/even numbers using the traditional if-else construct:

#include <stdio.h>

int main() {
   int a = 10;

   if (a % 2 == 0) {
      printf("%d is Even\n", a);
   } else {
      printf("%d is Odd\n", a);
   }
   
   return 0;
}

Output

10 is Even

Example 3

This program compares two variables, a and b, and assigns the greater value to c using the ternary operator:

#include <stdio.h>

int main() {
   int a = 100, b = 20, c;

   c = (a >= b) ? a : b;

   printf("a: %d b: %d c: %d\n", a, b, c);

   return 0;
}

Output

a: 100 b: 20 c: 100

Example 4

The equivalent program using if-else statements for the same purpose:

#include <stdio.h>

int main() {
   int a = 100, b = 20, c;

   if (a >= b) {
      c = a;
   } else {
      c = b;
   }
   printf("a: %d b: %d c: %d\n", a, b, c);

   return 0;
}

Output

a: 100 b: 20 c: 100

Example 5

When you need to include multiple statements in the true and/or false operand of the ternary operator, separate them with commas:

#include <stdio.h>

int main() {
   int a = 100, b = 20, c;

   c = (a >= b) ? (printf("a is larger "), c = a) : (printf("b is larger "), c = b);
   
   printf("a: %d b: %d c: %d\n", a, b, c);

   return 0;
}

Output

a is larger a: 100 b: 20 c: 20

Example 6

The equivalent program using if-else statements:

#include <stdio.h>

int main() {
   int a = 100, b = 20, c;

   if(a >= b) {
      printf("a is larger \n");
      c = a;
   } else {
      printf("b is larger \n");
      c = b;
   }
   printf("a: %d b: %d c: %d\n", a, b, c);

   return 0;
}

Output

a is larger
a: 100 b: 20 c: 100

Nested Ternary Operator

The ternary operator can be nested just like if-else statements. The syntax is:

exp1 ? (exp2 ? expr3 : expr4) : (exp5 ? expr6 : expr7)

C first checks if exp1 is true. If so, it evaluates exp2. If exp2 is true, the result is expr3; otherwise, it is expr4. If exp1 is false, it evaluates exp5 and returns either expr6 or expr7 based on its result.

Example 1

This program determines whether a number is divisible by 2 and 3, by 2 but not 3, by 3 but not 2, or neither:

#include <stdio.h>

int main() {
   int a = 15;
   printf("a: %d\n", a);

   (a % 2 == 0) ? (
      (a % 3 == 0) ? printf("divisible by 2 and 3") : printf("divisible by 2 but not 3")
   ) : (
      (a % 3 == 0) ? printf("divisible by 3 but not 2") : printf("not divisible by 2, not divisible by 3")
   );
   
   return 0;
}

Output

Try different values:

a: 15
divisible by 3 but not 2

a: 16
divisible by 2 but not 3

a: 17
not divisible by 2, not divisible by 3

a: 18
divisible by 2 and 3

Example 2

Here’s the same logic using if-else statements:

#include <stdio.h>

int main() {
   int a = 15;
   printf("a: %d\n", a);

   if(a % 2 == 0) {
      if (a % 3 == 0) {
         printf("divisible by 2 and 3");
      } else {
         printf("divisible by 2 but not 3");
      }
   } else {
      if(a % 3 == 0) {
         printf("divisible by 3 but not 2");
      } else {
         printf("not divisible by 2, not divisible by 3");
      }
   }
   
   return 0;
}

Output

a: 15
divisible by 3 but not 2