Static variable in c/c++

[Subrat 4708266]

I am in problem with static variable.Please help me. Program: file1.h int x = 10; file2.cpp #include "file1.h" #include "stdio.h" extern int x; void main() { printf("%d",x); } o/p: Error(Unresolved external symbol)... As per my knlowledge is consern I know to access x I have to use extern.But it is giving error.I want to know whts there reseaon? Compiler: vc++ 2005(8.0ver)

[montiee]

Technically "x" isn't an extern the way you've done it. You don't need the extern keyword in file2.cpp. Extern is meant to imply that the variable is defined externally to the files that are referencing it. Since you've defined x in the header and then included it it isn't defined externally. Also you aren't using any static variables whatsoever in the example you've provided. I think you really need to find a basic C primer on the net talking about extern and static variable and read through that since you are missing some fundemental understandings. No point writing code until you clear that up.

[Subrat 4708266]

Please modify the code by which I can access x declared in file1.h in file2.cpp. Again give me one fantastic example of usages of keyword extern.Please don't give example like below... extern int x; fun() { printf("%d", x); } int x = 80; fun2(){ printf("%d", x); }

[montiee]

file1.c ------- int counter = 1; file2.h ------- extern int counter; file2.c --------- #include "file2.h" void countToTen() { while (counter <= 10) { printf("%d\n", counter++); } } Notice that counter is defined in the file.c file hence to access it we need to define it as external to our file2.c file that uses it. Hope that gives you an idea about extern vars. Similar principle applies to extern functions. You really need to read some books on the topic.

[Subrat 4708266]

Thanks a lot. It'd be great if you are sending me some useful links.