What is "-=" ???

There was a RPG source code written in c++ that had this:

Code:

---

y -= 1;

---

If you guys want I'll add in the whole(still uncomplete) source code, but I figured it wouldn't matter.

But what is a subtraction sign doing next to an equal sign??

It means:

Code:

---

y = y - 1;

---

Lookup "assignment operator" in your C++ book.

Thanks guys! Much appreciated!