(float) or (float*) wrt sizeOf()

This is a discussion on (float) or (float*) wrt sizeOf() within the C Programming forums, part of the General Programming Boards category; I keep seeing these calls when allocating memory and its confusing the **** out of me. Please can someone clarify ...

  1. #1
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    (float) or (float*) wrt sizeOf()

    I keep seeing these calls when allocating memory and its confusing the **** out of me. Please can someone clarify for me.

    Here are the two calls that are confusing me.

    malloc(arraySizeX*sizeof(float*))
    malloc(arraySizeX*sizeof(float))

    Whats the difference between
    sizeof(float*)
    and
    sizeof(float)

    More precisely what affect does the * symbol have on the parameter float?

    Not sure if Its a typo I keep seeing pop up when I see this function used (mostly in malloc() calls) or if these two calls have different results?
    Thank you.

  2. #2
    Webhead Spidey's Avatar
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    More precisely what affect does the * symbol have on the parameter float?
    The * symbol is representative of the pointer in C.
    A pointer is basically a variable which holds the address of another variable in the program.\

    eg:

    Code:
    float x = 5.0;
    float* px = &x;// & is the address of operator which returns the address of x
    printf("The variable x = %f lives at the adress %p",*px, px);//*px dereferences the pointer and returns the value the pointer is pointing to
    a pointer is usually 4 bytes in memory.

    in your example
    Code:
    malloc(arraySizeX*sizeof(float*))
    is usually used when allocating memory to a pointer to a pointer or perhaps a 2D array.

    and

    Code:
    malloc(arraySizeX*sizeof(float)
    is used when allocating memory for a pointer, or in your case and array.

  3. #3
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    Awesome. That cleared it up. Thank you for the help.

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