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    <p>After looking at the answers and comments, I think there are a few more things to clarify:</p> <ol> <li>If variables are defined / declared outside any function body in a compilation unit, you must specify the storage class , e.g. <code>static</code></li> <li>These variables will be put to BSS section of you executable file. And you'd better initialize then.</li> <li>When defining an array, you could use initializer <code>{...}</code> to initialize it. But you cannot use it in assignment statement.</li> <li><code>double rob_leftcolor[3] = {1.0, 0.0, 0.0}</code> is a definition, while <code>rob_leftcolor[3] = {1.0, 0.0, 0.0}</code> is an assignment, so you can not use initializer here.</li> <li>Please make sure you know the differences between declaration and definition in C.</li> </ol> <p>For storage class, consider the case below, without <code>static</code>, you are actually defining global variables:</p> <pre><code>// a1.c static double rob_size, rob_tilt; rob_leftcolor [3] = {1.0, 0.0, 0.0}; rob_rightcolor [3] = {0.0, 1.0, 0.0}; int main(int argc, char** argv) { rob_size = 1.0; rob_tilt = 0.0; return 0; } // a2.c rob_leftcolor [3] = {1.0, 0.0, 0.0}; </code></pre> <p>Then compile &amp; link them:</p> <pre><code>$ gcc -c a1.c a1.c:2:1: warning: data definition has no type or storage class [enabled by default] a1.c:3:1: warning: data definition has no type or storage class [enabled by default] $ gcc -c a2.c a2.c:1:1: warning: data definition has no type or storage class [enabled by default] $ gcc -o a a1.o a2.o a2.o:(.data+0x0): multiple definition of `rob_leftcolor' a1.o:(.data+0x0): first defined here collect2: error: ld returned 1 exit status </code></pre>
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    1. PO"Expected expression before ' { ' token"
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    1. COCould you expand on the first concept of specifying the storage class?
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    2. COYou do not have to specify a storage class.
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      1. USCharlie Burns
    3. COA storage class defines the scope (visibility) and life time of variables and/or functions within a C Program. There are following storage classes which can be used in a C Program : `auto`, `register`, `static`, `extern`. Actually `auto` is the default one, and you don't need to explicitly specify a variable with `auto` storage class. You could refer to "The C Programming Language" for storage class.
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