---
# System prepended metadata

title: IO event

---

# IO event
### _Name_ 
add_listener - listen to the key inputs from hardware and interact with game program

### _Signature_
```C
void add_listener(int event, void *handler)
```

### _Parameters_
int event - event type flag
void* handler: callback function of the event

### _Return Value_
On success return 1, On failure return -1
