extern is funny....

[areza123]

hi i have 2 C++ files say a.cpp and a main.cpp;lets say a function a() is defined and implemented in a.cpp ; i need to call this function in main()
then i should declare a() as extern void a() in main.cpp ; but this works even without extern. So what is the use of extern ?

 

[dds82]

You don't need to declare functions as extern. You use extern with variables, like this:

If you have a global variable

int var1;

declared in a.cpp, and you want to reference that variable in main.cpp, you'd write

extern int var1;

at the top of main.cpp. Now you can use var1 in main.cpp and it will have the same value as the var1 in a.cpp.

HTH