Pointer Arithmetic

Pointer arithmetic is very important to understand, if you want to have complete knowledge of pointer. In this topic we will study how the memory addresses change when you increment a pointer.


16 bit Machine ( Turbo C )

In a 16 bit machine, size of all types of pointer, be it int*, float*, char* or double* is always 2 bytes. But when we perform any arithmetic function like increment on a pointer, changes occur as per the size of their primitive data type.

Size of datatypes on 16-bit Machine :

Type
Size(bytes)
int or signed int 2
char 1
long 4
float 4
double 8
long double 10

Examples for Pointer Arithmetic

Now lets take a few examples and understand this more clearly.

int* i;
i++;

In the above case, pointer will be of 2 bytes. And when we increment it, it will increment by 2 bytes because intis also of 2 bytes.

 

float* i;
i++;

In this case, size of pointer is still 2 bytes. But now, when we increment it, it will increment by 4 bytes becausefloat is of 4 bytes.

 

double* i;
i++;

Similarly, in this case, size of pointer is still 2 bytes. But now, when we increment it, it will increment by 8 bytes because its data type is double.


32 bit Machine ( Visual Basic C++ )

The concept of pointer arithmetic remains exact same, but the size of pointer and various datatypes is different in a 32 bit machine. Pointer in 32 bit machine is of 4 bytes.

And, following is a table for Size of datatypes on 32-bit Machine :

Type
Size(bytes)
int or signed int 4
char 2
long 8
float 8
double 16
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