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18 <p>Deep sentence:
20 applied to an external variable or function,
21 limits the scope of that object
22 to the rest of the source file being compiled.
26 which must be external so they can be shared,
27 yet which should not be visible
29 </blockquote>So we can have three kinds of declarations:
30 local to one function,
31 restricted to one source file,
32 or global across potentially many source files.
33 We can imagine other possibilities,
34 but these three cover most needs.
36 Applied to a local variable
37 (one inside of a function),
38 it modifies the lifetime (``duration'') of the variable
39 so that it persists for as long as the program does,
40 and does not disappear between invocations of the function.
41 Applied to a variable outside of a function
42 (or to a function)
47 although any file which wishes to use it will generally need an
51 from accessing a variable or function;
53 they'll get errors about ``undefined externals.''
54 </p><p>The rules for declaring and defining functions and global variables,
56 are admittedly complicated and somewhat confusing.
57 You don't need to memorize all of the rules right away:
58 just use simple declarations and definitions at first,
59 and as you find yourself needing some of the more complicated
61 the rules will begin to make more sense.
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63 <p>
64 Read sequentially:
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