How to change process memory?

Question

C++ / C#

I decided the other day to try out an interesting topic, namely memory hacking.
I watched a tutorial ( https://www.youtube.com/watch?v=I0zPwg4iUDk), more or less adequate, where a person explains in detail what and how to do, but after watching the video several times and rewriting the code, I realized that I had nothing does not work. Through a simple debugging, I realized that the problematic place is in the memory entry itself.
In the cheat engine at this moment of the video (2:03), the value in the calculator does not change for me, that is, if it becomes 40, then I still have 20.

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#include
#include
using std::cout;
using std::cerr;
using std::endl;

int main() {
int val = 200;
HWND hWnd = FindWindowA(0, "Calculator");
if (hWnd != 0) cout << "All things good. We are ready to get started!" <<endl;
else cerr << "Cannot find calculator app running." <<endl;
DWORD pID;
GetWindowThreadProcessId(hWnd, &pID);
HANDLE hProc = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pID);
if (hProc) cout << "Still doin' good." <<endl;
else cerr << "Cannot find the process!" <<endl;
int success = WriteProcessMemory(hProc, (LPVOID)0x278AEC16570, &val, (DWORD)sizeof(val), NULL);
if (success > 0) cout << "Congratulations. You got that!" <<endl;
else cerr << "Try something else!
well, the output:
All things good. We are ready to get started!
Still doin' good.
Try something else!

Answer 1

I don’t change the value in the calculator, that is, if it becomes 40, then I still have 20.

So you found the wrong address. Try something else!