Effect of Ptr++ on pointer

Ptr++ increases the pointer by sizeof(the type it points to) bytes, so that it points to the next element of that type. The compiler scales the increment automatically.

• char *: 1 byte
• int *: 4 bytes (typical)
• double *: 8 bytes
• pointer to a structure: sizeof(struct), including any padding

#include <stdio.h>

struct rec { char name[10]; int roll; };

int main(void)
{
    char c[2]; int i[2]; double d[2]; struct rec r[2];
    char *pc = c; int *pi = i; double *pd = d; struct rec *pr = r;

    printf("char   : %ld byte(s)\n", (long)((char *)(pc + 1) - (char *)pc));
    printf("int    : %ld byte(s)\n", (long)((char *)(pi + 1) - (char *)pi));
    printf("double : %ld byte(s)\n", (long)((char *)(pd + 1) - (char *)pd));
    printf("struct : %ld byte(s)\n", (long)((char *)(pr + 1) - (char *)pr));
    return 0;
}

Output (typical 64-bit system):

char   : 1 byte(s)
int    : 4 byte(s)
double : 8 byte(s)
struct : 16 byte(s)

The structure takes 16 bytes: 10 for name, 2 bytes of padding so that roll starts at a multiple of 4, and 4 for roll.