A global variable that is used by a C program file "file1.c" may be defined inside another C program file "file2.c" In order for the C compiler to use the correct encoding method to interpret the bits stored in a variable, it must know the data type The way I've always done this in my previous applications was to declare "extern unsigned int temp1;" in main.h and then #include main.h in both the .c files. Using extern is only of relevance when the program you're building consists of multiple source files linked together, where some of the variables defined, for example, in source file file1.c need to be referenced in other source files, such as file2.c.. Best way to declare and define global variables. Notice that inside function func_2() there is a local variable with the same name as a global variable. This is because the command Pay attention to the term used here : define and declare.
Global variables hold their values throughout the lifetime of your program and they can be accessed inside any of the functions defined for the program. The way I've always done this in my previous applications was to declare "extern unsigned int temp1;" in main.h and then #include main.h in both the .c files. Such variables are called global variables.

To properly access that global variable, Line 3 identifies the variable as an external int.

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Private self-hosted questions and answers for your enterpriseProgramming and related technical career opportunitiesRework the code to use something other than global variables - or retag the question as "C". It could be called a worldwide variable. That's why: don't declare extern in the consuming .cpp file. #include "myproject.h" This way the header file defines the variable as an extern in all of your c / cpp files so that it is visible to all of them but the variable is only actually declared and memory allocated for it in one place, in the .c file. Maybe I am misinterpreting what the code is doing.


Global Variables. This way, the compiler will not allocate memory blocks for it for now but do it later when meet with the real definition of this var.Fill in your details below or click an icon to log in: And common.h has been #included in main.c and… The variable also can be used by any function at any time. Declaring and naming global variables. What is the best way to do this? I don't see what you're describing to be the case with any of the Hi-Tech compilers I have handy. site design / logo © 2020 Stack Exchange Inc; user contributions licensed under Here’s an example of a global variable … In line 4, a and b are declared as two global variables of type int.The variable a will be automatically initialized to 0. For example： In the project, there are main.c、common.c and common.h. I'm just explaining what you would put in those files.also, file 1 should NOT be a header file, it should be a .c file. Forum Themes A global variable can be used in all functions. In the same way source2.h describes what is public available in source2.cpp.In one file you declare it as in source1.cpp, in the second you declare it as Of course you really don't want to be doing this and should probably post a question about what you are trying to achieve so people here can give you other ways of achieving it.Thanks for contributing an answer to Stack Overflow! I have multiple variables in my script file, say, var1, var2, var3.I want to declare them global variable.

A local variable can only be used in the function where it is declared. This type of variable could be called a universal variable. Stack Overflow works best with JavaScript enabled The count variable is then used in the second() function — specifically, at Line 7. #include "common.h" int global; int function(); int main() { global=42; function(); return 0; } source2.cpp Global Variables across multiple C files Say I want to use variable "unsigned int temp1" in two .c files (main.c and project.c).

Few variables are truly "global".If you want more info and explanation behind this : You should achieve that the compiler gets the same extern declaration for each compilation unit, that needs the declaration. A global variable can be accessed by any function. It can be used for both variables and function prototypes.If you use int i; in file2.c under main() then i will be treated as local auto variable not the same as defined in file1.cIf you want to use global variable i of file1.c in file2.c, then below are the points to remember:Thanks for contributing an answer to Stack Overflow! See the output, here the value of x is 100 which is the value of local variable x, so here we are unable to access global variable x. Stack Overflow works best with JavaScript enabled

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