Defining extern variables - MQL4 Documentation

MQL4 Reference Basics Variables Defining extern variables

Local variables
Formal parameters
Static variables
Global variables
Defining extern variables
Initialization of variables
External functions definition

The extern memory class defines an extern variable. The extern specifier is declared before a data type.

Example:

extern double InputParameter1 = 1.0;
extern color  InputParameter2 = red;

int init()
  {
   ...
  }

Extern variables determine inputs of the program, they are accessible from a program properties window. Arrays cannot represent themselves as extern variables.

Global variables Initialization of variables