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Unary operators in C

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Unary operators are the operators that perform operations on a single operand to produce a new value.

Types of unary operators

Types of unary operators are mentioned below:

  1. Unary minus ( – )
  2. Increment ( ++ )
  3. Decrement ( — )
  4. NOT ( ! )
  5. Addressof operator ( & )
  6. sizeof()

1. Unary Minus

The minus operator ( – ) changes the sign of its argument. A positive number becomes negative, and a negative number becomes positive.

 int a = 10;
int b = -a; // b = -10

Unary minus is different from the subtraction operator, as subtraction requires two operands.

Below is the implementation of the unary minus (-) operator:

C

#include <stdio.h>
 
int main()
{
    // declaring a positive integer
    int positiveInteger = 100;
    // using - sign to make the value of positive integers
    // to negative
    int negativeInteger = -positiveInteger;
 
    printf("Positive Integer = %d\n", positiveInteger);
    printf("Negative Integer = %d", negativeInteger);
    return 0;
}

                    

Output
Positive Integer = 100
Negative Integer = -100

2. Increment

The increment operator ( ++ ) is used to increment the value of the variable by 1. The increment can be done in two ways:

2.1 prefix increment

In this method, the operator precedes the operand (e.g., ++a). The value of the operand will be altered before it is used.

Example:

  int a = 1;
int b = ++a; // b = 2

2.2 postfix increment

In this method, the operator follows the operand (e.g., a++). The value operand will be altered after it is used.

Example:

 int a = 1;
int b = a++; // b = 1
int c = a; // c = 2

Below is the implementation of the increment ( ++ ):

C

// C program to illustrate increment
 
#include <stdio.h>
 
int main()
{
    int a = 5;
    int b = 5;
    printf("Pre-Incrementing a = %d\n", ++a);
    printf("Post-Incrementing b = %d", b++);
    return 0;
}

                    

3. Decrement

The decrement operator ( — ) is used to decrement the value of the variable by 1. The decrement can be done in two ways:

3.1 prefix decrement

In this method, the operator precedes the operand (e.g., – -a). The value of the operand will be altered before it is used.

Example:

  int a = 1;
int b = --a; // b = 0

3.2 postfix decrement

In this method, the operator follows the operand (e.g., a- -). The value of the operand will be altered after it is used.

Example:

 int a = 1;
int b = a--; // b = 1
int c = a; // c = 0

Below is the implementation of the decrement ( — ):

C

// C program to illustrate decrement
 
#include <stdio.h>
 
int main()
{
    int a = 5;
    int b = 5;
    printf("Pre-Decrementing a = %d\n", --a);
    printf("Post-Decrementing b = %d", b--);
    return 0;
}

                    

4. NOT ( ! )

The logical NOT operator ( ! ) is used to reverse the logical state of its operand. If a condition is true, then the Logical NOT operator will make it false.

Example:

   If x is true, then !x is false
If x is false, then !x is true

Below is the implementation of the NOT (!) operator:

C

// C program to illustrate NOT operator
#include <stdio.h>
 
int main()
{
 
    int a = 10;
    int b = 5;
 
    if (!(a > b))
        printf("b is greater than a\n");
    else
        printf("a is greater than b");
 
    return 0;
}

                    

Output
a is greater than b

5. Addressof operator ( & )

The addressof operator ( & ) gives an address of a variable. It is used to return the memory address of a variable. These addresses returned by the address-of operator are known as pointers because they “point” to the variable in memory.

Example:

    & gives an address on variable n
int a;
int *ptr;
ptr = &a; // address of a is copied to the location ptr.

Below is the implementation of the Addressof operator(&):

C

// C program to demonstrate the use of 'address-of(&)'
// operator
#include <stdio.h>
 
int main()
{
 
    int a = 20;
    printf("Address of a = %p", &a);
 
    return 0;
}

                    

Output
Address of a = 0x7fff78c3f37c

6. sizeof()

This operator returns the size of its operand, in bytes. The sizeof() operator always precedes its operand. The operand is an expression, or it may be a cast.

Note: The `sizeof()` operator in C++ is machine dependent. For example, the size of an ‘int’ in C++ may be 4 bytes in a 32-bit machine but it may be 8 bytes in a 64-bit machine.

Below is the implementation of sizeof() operator:

C

// C program to illustrate the sizeof operator
#include <stdio.h>
 
int main()
{
    // printing the size of double and int using sizeof
    printf("Size of double: %d\n", sizeof(double));
    printf("Size of int: %d\n", sizeof(int));
 
    return 0;
}

                    

Output
Size of double: 8
Size of int: 4




Last Updated : 26 Dec, 2023
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