Thread: Pointers...

  1. 09-14-2010 #1
    rehan
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    Pointers...

    Hi, i am a new one in programming, please help me in finding out the difference among the two statements.


    First syntax
    Code:
    volatile unsigned int *mec=(volatile unsigned int *)0x01f80000;

    Second Syntax
    Code:
    volatile unsigned int *mec;
mec=(volatile unsigned int *)0x01f80000;
  2. 09-14-2010 #2
    grumpy
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    Look up the difference between initialisation (or initialization for those challenged with the english language) and assignment.
    Right 98% of the time, and don't care about the other 3%.

    If I seem grumpy or unhelpful in reply to you, or tell you you need to demonstrate more effort before you can expect help, it is likely you deserve it. Suck it up, Buttercup, and read this, this, and this before posting again.
  3. 09-14-2010 #3
    rehan
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    @grumpy if u can further explain it, it will be helpful
  4. 09-14-2010 #4
    AnishaKaul
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    Code:
    volatile unsigned int *mec;
mec=(volatile unsigned int *)0x01f80000;
    Here, 1st statement is declaration of mec and 2nd one is definition of mec !

    Code:
    volatile unsigned int *mec=(volatile unsigned int *)0x01f80000;
    Here the declaration and the definition have been clubbed together !
  5. 09-14-2010 #5
    orientuser
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    If mec is an auto local variable(no static precedes volatile unsigned int), they are identical.
  6. 09-15-2010 #6
    grumpy
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    Quote Originally Posted by rehan View Post
    @grumpy if u can further explain it, it will be helpful
    I'd argue you will benefit more by working out the answer for yourself. I've given you a hint to get you started on that.

    AnishaKaul, you're barking up the wrong tree.
    Right 98% of the time, and don't care about the other 3%.

    If I seem grumpy or unhelpful in reply to you, or tell you you need to demonstrate more effort before you can expect help, it is likely you deserve it. Suck it up, Buttercup, and read this, this, and this before posting again.
  7. 09-15-2010 #7
    Elysia
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    Quote Originally Posted by AnishaKaul View Post
    Code:
    volatile unsigned int *mec;
mec=(volatile unsigned int *)0x01f80000;
    Here, 1st statement is declaration of mec and 2nd one is definition of mec !

    Code:
    volatile unsigned int *mec=(volatile unsigned int *)0x01f80000;
    Here the declaration and the definition have been clubbed together !
    Incorrect.

    volatile unsigned int* mec;

    Is both a declaration and a definition.
    It does not need an assignment to be a definition. And assignment certainly isn't a definition.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.
  8. 09-15-2010 #8
    AnishaKaul
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    I apologize for the mis-information in the post number 4 !
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