C Pointers

pointers.c

    

// * - indirection operator
    int *pNumber = NULL, myNum = 1;
    char *my_str = "hello";
    long num1 = 0L, num2 = 0L, *pNum = NULL;

    if (pNumber == NULL)
        printf("pNumber is currently NULL\n");
    pNumber = &myNum;
    for (; myNum<100; myNum++)
        ;
    printf("result: %i\n", *pNumber);

    // Out of bounds error occurs if we loop past the index length of my_str
    // Decrement too far & will get an under bounds error
    for (int i=0; i<5; i++)
        printf("result: %c\n", *my_str++);

    printf("my_str's address: %p\n", &my_str);

    int number = 0;
    int *pnumber = NULL;

    number = 10;

    printf("numbers address: %p\n", &number);
    printf("number's value: %d\n\n", number);

    pnumber = &number;

    printf("pnumber's address %p\n", (void*)&pnumber); // to void for some systems might error
    printf("pnumber's size: %d bytes \n", sizeof(pnumber)); // bytes
    printf("pnumber's value: %p\n", pnumber); // address
    printf("value pointed to: %d\n\n\n", *pnumber);

    /* ====================================================================== */
    /* Using Pointers */
    /* ====================================================================== */
    long num1 = 0L;
    long num2 = 0L;
    long *pnum = NULL;

    pnum = &num1;
    *pnum = 2L;
    printf("num1 = %ld\n", num1); // 2

    ++num2;
    printf("num2 = %ld\n", num2);  // 1

    num2 += *pnum;
    printf("num2 = %ld\n\n\n", num2); // 3

    ++*pnum;
    printf(
           "num1 = %ld\n"
           "num2 = %ld\n"
           "*pnum = %ld\n\n\n"


          ,num1, num2, *pnum
        );