Thread: why this code Works.

  1. #1
    Registered User
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    Feb 2014
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    why this code Works.

    i asked a newbie to write me a program to print from 1 to 100.
    He gave me this code
    Code:
    #include <stdio.h>
    int main()
    {
    int i,A[100];
    for(i = 1; i <= 100; i++)
    printf("%d\n",A[100]);
    }
    It WORKED..
    Ive ran the code on ubuntu and on windows perfectly.
    I dont understand why it works.
    Can any one help.

  2. #2
    Master Apprentice phantomotap's Avatar
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    Jan 2008
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    5,108
    O_o

    That code does not work; that code only appears to work under specific circumstances.

    Soma
    “Salem Was Wrong!” -- Pedant Necromancer
    “Four isn't random!” -- Gibbering Mouther

  3. #3
    Registered User
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    Oct 2006
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    3,445
    You're experiencing undefined behavior. The C compiler(s) that you are using places the value of i in the memory location just past the end of your array. There is no guarantee that this will happen all the time, and you should certainly not depend on this behavior.
    What can this strange device be?
    When I touch it, it gives forth a sound
    It's got wires that vibrate and give music
    What can this thing be that I found?

  4. #4
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    Was this question really worth cross-posting?

  5. #5
    Registered User Alpo's Avatar
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    Apr 2014
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    How could it even print a different number each time? Shouldn't it just print a single garbage number 99 times?

    Edit: just caught on to what Elkvis said, I got it.

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