MFC Global Variables: Definition & Usage Guide

Global variables in MFC (Microsoft Foundation Class) can be accessed anywhere in the application because they are variables defined within the scope of the entire application. To define and use global variables, follow these steps:

1. Define global variables in the header file of the application (typically in xxx.cpp file). For example, in the xxx.cpp file, you can define a global variable like this:

int g_nGlobalVariable = 0;

1. In places where you need to access this global variable, you can directly use it. For example, in any part of the application, you can access and modify the value of the global variable in this way:

g_nGlobalVariable = 10;

It should be noted that using global variables in a multithreaded environment can lead to potential thread safety issues. Therefore, in a multi-threaded application, mutex locks or other synchronization mechanisms should be used to protect access to global variables. Additionally, excessive use of global variables should be avoided in program design, and one can consider using static member variables of a class instead of global variables.