1# Thread Model (FA Model) 2 3 4There are three types of threads in the FA model: 5 6 7- Main thread 8 9 Manages other threads. 10 11- Ability thread 12 - One ability thread for each ability. 13 - Distributes input events. 14 - Draws the UI. 15 - Invokes application code callbacks (event processing and lifecycle callbacks). 16 - Receives messages sent by the worker thread. 17 18- Worker thread 19 20 Performs time-consuming operations 21 22 23Based on the OpenHarmony thread model, different services run on different threads. Service interaction requires inter-thread communication. Threads can communicate with each other in Emitter or Worker mode. Emitter is mainly used for event synchronization between threads, and Worker is mainly used to execute time-consuming tasks. 24 25 26> **NOTE** 27> 28> The FA model provides an independent thread for each ability. Emitter is mainly used for event synchronization within the ability thread, between a pair of ability threads, or between the ability thread and worker thread. 29