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C Programming Language

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Pointers Arithmatic Operations in C

Pointer variables are used to store address of variables. Address of any variable is an unsigned integer value i.e., it is a numerical value. So we can perform arithematic operations on pointer values. But when we perform arithematic operations on pointer variable, result depends on the amount of memory required by the variable to which the pointer is pointing.

In c programming language, we can perform the following arithematic operations on pointers...

  1. Addition
  2. Subtraction
  3. Increment
  4. Decrement
  5. Comparison

Addition Operation on Pointer

In c programming language, the addition operation on pointer variables is calculated using the following formula...

AddressAtPointer + ( NumberToBeAdd * BytesOfMemoryRequiredByDatatype )

Example Program

void main()
{
   int a, *intPtr ;
   float b, *floatPtr ;
   double c, *doublePtr ;
   clrscr() ;
   intPtr = &a ;  // Asume address of a is 1000
   floatPtr = &b ;  // Asume address of b is 2000
   doublePtr = &c ;  // Asume address of c is 3000
   
   intPtr = intPtr + 3 ;  // intPtr = 1000 + ( 3 * 2 )
   floatPtr = floatPtr + 2 ;  // floatPtr = 2000 + ( 2 * 4 )
   doublePtr = doublePtr + 5 ;  // doublePtr = 3000 + ( 5 * 6 )
   
   printf("intPtr value : %u\n", intPtr) ;
   printf("floatPtr value : %u\n", floatPtr) ;
   printf("doublePtr value : %u", doublePtr) ;
   
   getch() ;
}

Output:

switch in c programming

Subtraction Operation on Pointer

In c programming language, the subtraction operation on pointer variables is calculated using the following formula...

AddressAtPointer - ( NumberToBeAdd * BytesOfMemoryRequiredByDatatype )

Example Program

void main()
{
   int a, *intPtr ;
   float b, *floatPtr ;
   double c, *doublePtr ;
   clrscr() ;
   intPtr = &a ;  // Asume address of a is 1000
   floatPtr = &b ;  // Asume address of b is 2000
   doublePtr = &c ;  // Asume address of c is 3000
   
   intPtr = intPtr - 3 ;  // intPtr = 1000 - ( 3 * 2 )
   floatPtr = floatPtr - 2 ;  // floatPtr = 2000 - ( 2 * 4 )
   doublePtr = doublePtr - 5 ;  // doublePtr = 3000 - ( 5 * 6 )
   
   printf("intPtr value : %u\n", intPtr) ;
   printf("floatPtr value : %u\n", floatPtr) ;
   printf("doublePtr value : %u", doublePtr) ;
   
   getch() ;
}

Output:

pointers in c programming

Increment & Decrement Operation on Pointer

The increment operation on pointer variable is calculated as follows...

AddressAtPointer + NumberOfBytesRequiresByDatatype

Example Program

void main()
{
   int a, *intPtr ;
   float b, *floatPtr ;
   double c, *doublePtr ;
   clrscr() ;
   intPtr = &a ;  // Asume address of a is 1000
   floatPtr = &b ;  // Asume address of b is 2000
   doublePtr = &c ;  // Asume address of c is 3000
   
   intPtr++ ;  // intPtr = 1000 + 2
   floatPtr++ ;  // floatPtr = 2000 + 4
   doublePtr++ ;  // doublePtr = 3000 + 6
   
   printf("intPtr value : %u\n", intPtr) ;
   printf("floatPtr value : %u\n", floatPtr) ;
   printf("doublePtr value : %u", doublePtr) ;
   
   getch() ;
}

Output:

pointers in c programming

The decrement operation on pointer variable is calculated as follows...

AddressAtPointer - NumberOfBytesRequiresByDatatype

Example Program

void main()
{
   int a, *intPtr ;
   float b, *floatPtr ;
   double c, *doublePtr ;
   clrscr() ;
   intPtr = &a ;  // Asume address of a is 1000
   floatPtr = &b ;  // Asume address of b is 2000
   doublePtr = &c ;  // Asume address of c is 3000
   
   intPtr-- ;  // intPtr = 1000 - 2
   floatPtr-- ;  // floatPtr = 2000 - 4
   doublePtr-- ;  // doublePtr = 3000 - 6
   
   printf("intPtr value : %u\n", intPtr) ;
   printf("floatPtr value : %u\n", floatPtr) ;
   printf("doublePtr value : %u", doublePtr) ;
   
   getch() ;
}

Output:

pointers in c programming

Comparison of Pointers

The comparison operation is perform between the pointers of same datatype only. In c programming language, we can use all comparison operators (relational operators) with pointers.

We can't perform multiplication and division operations on pointers.


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