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

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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