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C Declarations and Definitions | Microsoft Docs |
11/04/2016 |
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article |
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575f0c9b-5554-4346-be64-b2129ca9227f |
8 |
mikeblome |
mblome |
ghogen |
A "declaration" establishes an association between a particular variable, function, or type and its attributes. Overview of Declarations gives the ANSI syntax for the declaration nonterminal. A declaration also specifies where and when an identifier can be accessed (the "linkage" of an identifier). See Lifetime, Scope, Visibility, and Linkage for information about linkage.
A "definition" of a variable establishes the same associations as a declaration but also causes storage to be allocated for the variable.
For example, the main, find, and count functions and the var and val variables are defined in one source file, in this order:
int main() {}
int var = 0;
double val[MAXVAL];
char find( fileptr ) {}
int count( double f ) {}
The variables var and val can be used in the find and count functions; no further declarations are needed. But these names are not visible (cannot be accessed) in main.