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C - External variables2

From EdWiki

External variables ...

  • If the program is in several source files, and a global variable is defined in file1.c and used in file2.c and file3.c, then extern declarations are needed in file2.c and file3.c to connect the occurrences of the variable.
  • The ANSI C standard calls this as external linkage.
  • In C, all functions are global and provide external linkage by default.