pointer issue

This is a discussion on pointer issue within the C Programming forums, part of the General Programming Boards category; I have two questions, 1 Code: main(){ int i =257; int *iptr =&i; printf (“%d %d”,*((char*)iptr),* ((char *)iptr+1)); } the ...

  1. #1
    Registered User
    Join Date
    Jul 2008

    pointer issue

    I have two questions,

    int i =257;
    int *iptr =&i;
    printf (“%d  %d”,*((char*)iptr),* ((char *)iptr+1));
    the output is 1 1

    here, iptr at first should print the value stored in first 8 bits of variable i and in next it should print value of second 8 bit block.
    would you please explain why the out put is so?

    extern int iExtern;
    iExtern = 20;
    why there is an linker error, how should we use the variable so that the error wont come?

  2. #2
    and the hat of sweating
    Join Date
    Aug 2007
    Toronto, ON
    What if you change it to:
    int i = 258;
    Think about what 257 looks like in binary.
    "I am probably the laziest programmer on the planet, a fact with which anyone who has ever seen my code will agree." - esbo, 11/15/2008

    "the internet is a scary place to be thats why i dont use it much." - billet, 03/17/2010

  3. #3
    Jack of many languages Dino's Avatar
    Join Date
    Nov 2007
    Katy, Texas
    1) you are casting your int into a char, and 257 as a char is 1.

    2) Prove there is a linker error. I see no link command and no linker error message.
    Mac and Windows cross platform programmer. Ruby lover.

    Quote of the Day
    12/20: Mario F.:I never was, am not, and never will be, one to shut up in the face of something I think is fundamentally wrong.

    Amen brother!

  4. #4
    Registered User
    Join Date
    Sep 2008
    Toronto, Canada
    There certainly is, Dino:
    test.obj : error LNK2001: unresolved external symbol "int iExtern"

    Try to be less sarcastic and more helpful.

  5. #5
    Registered User
    Join Date
    Oct 2008
    In 1 write out the integer 257 in binary and you will see why the output of your program 1 1 is correct.

    In 2 remove the extern qualifier so the scope of the variable iExtern becomes local instead of global and try not to use reserved keywords for variable names.

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