A C++ tutorial says this:
Yet there are programs that do change other program's memory while they're running (I'm thinking mainly of game cheaters). Is there an easy way to get the OS to allow you to get the address of a certain piece of data that's in another program's memory, and possibly change it?For instance, the operating system will probably prevent you from accessing memory that it knows your program doesn't own: this will cause your program to crash. If it let you use the memory, you could mess with the memory of any running program--for instance, if you had a document opened in Word, you could change the text! Fortunately, Windows and other modern operating systems will stop you from accessing that memory and cause your program to crash. To avoid crashing your program, you should always initialize pointers before you use them.