PointerLessonByWinHtut

1 Pointer

#include <stdio.h>
int main()
{

int arr[5]={10,30,20,50,60};
int *ptr1=&arr[0];// *ptr=arr;
int *ptr2= ptr1+3;
printf(" address of ptr1= %d\n",ptr1);

//pointer address = p + x*sizeof(*p);
//                = p + 3 * 4 ;
//                = 6356704 + 12 ;
//                = 6356716;>> which memory address?

printf(" address of index 1 : %d\n",&arr[1]);
printf(" address of index 2 : %d\n",&arr[2]);
printf(" address of index 3 : %d\n",&arr[3]);
printf(" address of index 4 : %d\n",&arr[4]);

printf(" value is %d \n",*ptr2); // output 50 ;


int *ptr3;
ptr3= ptr2-ptr1;// 6356716- 6356704 = 12 / 4 = 3
printf(" ptr2-ptr1 = %d",ptr3);

   return 10;
}

2 TypeCastingInPointer

//pointer type-casting int=> char , int=>float
#include<stdio.h>
int main()
{
    int arr[] = {10, 20, 30, 40, 50, 60};//5*4 = 20
    int *ptr1 = arr;
    int *ptr2 = arr + 5;
    printf("Number of elements between two pointer are: %d.\n",
                                (ptr2 - ptr1));
    printf("number of bytes between two pointers are: %d",
            (double*)ptr2-(double*)ptr1);
            // 1 bytes = 20/1=20 ; for char
            // 1 bytes = 20/4=5 ; for float
            // 1 bytes = 20/8=2 ; for double
            //first way
            //second way
            // x*sizeof(oragi)/sizeof(new);
            //= 5 *4 / 1 = 20

    return 0;
}

3 Array Treated As Pointer

#include<stdio.h>

void fun(int arr[],int sz){
int i=0;
//printf("the size of first index arr[] %d\n",sizeof(arr));
//int arr_size=sizeof(arr)/sizeof(arr[0]);

//printf("arr size is %d\n",arr_size);

for(i=0; i<sz;i++){
    printf("the value is %d\n",arr[i]);
}

}

int main(){
int arr[4]={10,20,30,40};

size_t sz=sizeof(arr)/sizeof(arr[0]);
printf("the size of our array is :%d\n",sz);
fun(arr,sz);

return 0;
}