Assignment vs. Initialization

This is a discussion on Assignment vs. Initialization within the C Programming forums, part of the General Programming Boards category; I'm studying for an exam and just came across a sentence: "Initialization isn't the same as assignment." What? I thought ...

  1. #1
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    Assignment vs. Initialization

    I'm studying for an exam and just came across a sentence: "Initialization isn't the same as assignment." What? I thought when you assigned a variable a value, you're initializing the variable. If not, could someone clarify assignment vs initialization?

    Thanks!

  2. #2
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    There is defference between defination and declaration its same as initaililization and assignment, when u initialize a variable it means u r making identify the variable to your compiler, but when you assign you get the adress assigned for that variable for your compiler.
    e.g. Intialization
    Code:
    int i;
    assignment
    Code:
    int i=0;
    or in OOPS

    Initialization
    Code:
    Object obj;
    Assignment:

    Code:
    Object obj = new Object( arg list );

  3. #3
    C++まいる!Cをこわせ! Elysia's Avatar
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    This is not true.
    This is also the C board, no such things as classes which is a C++ term.

    Code:
    int i;
    No initialization.

    Code:
    int i = 0;
    Initialization to 0.

    Code:
    int i; */ Initialization */
    i = 0; /* Assignment */
    I don't think initialization vs assignment has such a big impact in C. More so in C++.
    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.

  4. #4
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    Yes, and there are several cases where the difference is noticeable, particularly when it comes to structures and arrays.

    You can initialize an array or struct with constant values, e.g. :
    Code:
    struct blah
    {
       int x;
       char *s;
    };
    
    struct blah array[3] = { { 1, "One"}, {2, "Two"}, { 3, "Three" } };
    
    // However, this doesn't work:
    struct blah array[3];
    
    array = { { 1, "One"}, {2, "Two"}, { 3, "Three" } };
    
    // Also won't work:
    struct blah array[3];
    struct blah arr2[3];
    ...
    array = arr2;
    
    // This works, however
    array[1] = arr2[1];
    That covers both structure and array initialization. Essentially, the compiler is able to give a variable a value when it's defined, but not later - you can only assign one element at a time from an array for example, and you can not assign constant values directly to a struct as a list of element values, each element on it's own will have to be set.

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  5. #5
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    The problem with using syntax alone to define the term is that:
    Code:
    int i;
    would not be initialized and thus have an indeterminate value if i has automatic storage duration, but would be initialized to 0 if i has static storage duration.

    Perhaps we should just state:
    Initialization means providing an initial value to an object (where object means "a contiguous region of memory holding a value of some type"). Assignment means providing a new value to an object that has been initialized or that has an indeterminate value.
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    Oooh. So initialization is basically creating a variable and assigning it a value all in go, and assignment is changing the value of an already existing variable. It makes more sense when you say it like that.
    Last edited by arrgh; 05-06-2008 at 03:12 AM.

  7. #7
    C++まいる!Cをこわせ! Elysia's Avatar
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    Yes. Or creating a variable with a value (initialization).
    I think laserlight's definition of initialization is a good one.
    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.

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