Changing a program from another program?

I have a question is it possible to change the execution of one program with another?

Such as if there is a program which does something like this:

Code:

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char a[10];
void abc()
{
a = "Hello";
cout<<a;
abc();
}

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how would i write a program that changes a to Dog??

I don't think it's possible to create a program that can actually change the value to dog, as the value has already been set. You could consider creating a .txt file that can be read (and changed by you if needed) to give a the value of your choice (dog). So the value could "be set" from outside the program itself.

You could even create another program to write this file, choosing the value to change the variable to. Though it's not a permanent change and obviously won't work if you delete the .txt file with the value in. So it doesn't change it as such, just (temporarily) gives it a value from outside the program in effect.

i undeerstand and know how to do this but im trying to find out if there is a way to change it even if its not programmed to be changed like some way to force the application to change

Quote:

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Originally Posted by Jake.c

I don't think it's possible to create a program that can actually change the value to dog, as the value has already been set. You could consider creating a .txt file that can be read (and changed by you if needed) to give a the value of your choice (dog). So the value could "be set" from outside the program itself.

You could even create another program to write this file, choosing the value to change the variable to. Though it's not a permanent change and obviously won't work if you delete the .txt file with the value in. So it doesn't change it as such, just (temporarily) gives it a value from outside the program in effect.

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Quote:

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Originally Posted by kakayoma

i undeerstand and know how to do this but im trying to find out if there is a way to change it even if its not programmed to be changed like some way to force the application to change

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Give it a good lecture? :p

Seriously though - sure, anything's possible. Is it trivial or even practical to do so? Of course not.

Why would you want to do this, anyway? If it's open-source, just recompile it. If it isn't then you probably don't have any business messing with it in the first place.

Yes it is possible and it isn't all that hard.

You'll need to look into the Windows Functions ReadProcessMemory and WriteProcessMemory. You also need a way to get the process handle, but I'll leave that up to you.

No, that is the easy part. The hard part comes later when figuring out what to change.