C - decrement operator

The decrement (--) is an unary operator in C and hence acts upon a single operand to produce a new value. It has two variant:

• Pre-decrement: Decreases the value of the operand by 1, then returns the operand.
• Post-decrement: Returns the operand, then decreases the value of the operand by 1.

Example: Pre-decrement operator

The example below describes the usage of pre-decrement operator.

#include <stdio.h>
 
int main (){
  int x = 10;
  int y = 20;
  int z;

  //below expression is equivalent to
  //x = x - 1; z = x + y;
  z = --x + y;    

  //Displaying the result
  printf("x = %d\n", x);
  printf("y = %d\n", y);
  printf("z = %d\n", z);
  return 0;
}

The output of the above code will be:

x = 9
y = 20
z = 29

Example: Post-decrement operator

The example below describes the usage of post-decrement operator.

#include <stdio.h>
 
int main (){
  int x = 10;
  int y = 20;
  int z;

  //below expression is equivalent to
  //z = x + y; x = x - 1; 
  z = x-- + y;    

  //Displaying the result
  printf("x = %d\n", x);
  printf("y = %d\n", y);
  printf("z = %d\n", z);
  return 0;
}

The output of the above code will be:

x = 9
y = 20
z = 30