C Programming Tutorial
In C pointer holds address of a value, so there can be arithmetic operations on the pointer variable. Following arithmetic operations are possible on pointer in C language:
- Increment
- Decrement
- Addition
- Subtraction
- Comparison
Incrementing Pointer in C
Incrementing a pointer is used in array because it is contiguous memory location. Moreover, we know the value of next location.
Increment operation depends on the data type of the pointer variable. The formula of incrementing pointer is given below:
new_address= current_address + i * size_of(data type)
32 bit
For 32 bit int variable, it will increment to 2 byte.
64 bit
For 64 bit int variable, it will increment to 4 byte.
Let's see the example of incrementing pointer variable on 64 bit OS.
#include<stdio.h>
int main(){
int number=50;
int *p;//pointer to int
p=&number;//stores the address of number variable
printf("Address of p variable is %u \n",p);
p=p+1;
printf("After increment: Address of p variable is %u \n",p);
return 0;
}
Output
Address of p variable is 3214864300
After increment: Address of p variable is 3214864304
Decrementing Pointer in C
Like increment, we can decrement a pointer variable. The formula of decrementing pointer is given below:
new_address= current_address - i * size_of(data type)
32 bit
For 32 bit int variable, it will decrement to 2 byte.
64 bit
For 64 bit int variable, it will decrement to 4 byte.
Let's see the example of decrementing pointer variable on 64 bit OS.
#include <stdio.h>
void main(){
int number=50;
int *p;//pointer to int
p=&number;//stores the address of number variable
printf("Address of p variable is %u \n",p);
p=p-1;
printf("After decrement: Address of p variable is %u \n",p);
}
Output
Address of p variable is 3214864300
After decrement: Address of p variable is 3214864296
C Pointer Addition
We can add a value to the pointer variable. The formula of adding value to pointer is given below:
new_address= current_address + (number * size_of(data type))
32 bit
For 32 bit int variable, it will add 2 * number.
64 bit
For 64 bit int variable, it will add 4 * number.
Let's see the example of adding value to pointer variable on 64 bit OS.
#include<stdio.h>
int main(){
int number=50;
int *p;//pointer to int
p=&number;//stores the address of number variable
printf("Address of p variable is %u \n",p);
p=p+3; //adding 3 to pointer variable
printf("After adding 3: Address of p variable is %u \n",p);
return 0;
}
Output
Address of p variable is 3214864300
After adding 3: Address of p variable is 3214864312
As you can see, address of p is 3214864300. But after adding 3 with p variable, it is 3214864312 i.e. 4*3=12 increment. Since we are using 64 bit OS, it increments 12. But if we were using 32 bit OS, it were incrementing to 6 only i.e. 2*3=6. As integer value occupies 2 byte memory in 32 bit OS.
C Pointer Subtraction
Like pointer addition, we can subtract a value from the pointer variable. The formula of subtracting value from pointer variable is given below:
new_address= current_address - (number * size_of(data type))
32 bit
For 32 bit int variable, it will subtract 2 * number.
64 bit
For 64 bit int variable, it will subtract 4 * number.
Let's see the example of subtracting value from pointer variable on 64 bit OS.
#include<stdio.h>
int main(){
int number=50;
int *p;//pointer to int
p=&number;//stores the address of number variable
printf("Address of p variable is %u \n",p);
p=p-3; //subtracting 3 from pointer variable
printf("After subtracting 3: Address of p variable is %u \n",p);
return 0;
}
Output
Address of p variable is 3214864300
After subtracting 3: Address of p variable is 3214864288
You can see after subtracting 3 from pointer variable, it is 12 (4*3) less than the previous address value.
