Why do we have pointers other than void

Question

I know that we have different pointers like int, float, and char. A void pointer is the only pointer which can hold all o

Answer 1

When you iterate through the memory block pointed to by a pointer, it's necessary to know the size of the data type the memory contains. Say you have two pointers, a charcharptr and an intintptr, both pointing at memory at byte X. charptr+1 will point to the byte X+1, while intptr+1 will point to byte X+4.

A quick and dirty piece of badly written code to illustrate that:

#include 

int main()
{
    char * cptr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    short * sptr = (short*)cptr;
    int * iptr = (int*)cptr;
    long long * lptr = (long long*)cptr;

    printf ("CHAR: %d, +1: %d\n",cptr,cptr+1);
    printf ("SHORT: %d, +1: %d\n",sptr,sptr+1);
    printf ("INT: %d, +1: %d\n",iptr,iptr+1);
    printf ("LONG LONG: %d, +1: %d\n",lptr,lptr+1);
}

This should:

• generate warnings about casting pointers of different sizes (type safety),
• output identical numbers in the first column (all pointers point to the same address in memory), but different numbers in the 2nd column (which is base address + size of the pointer's type: 1, 2, 4 and 8 bytes).