What is stop and wait ARQ in error control ?

What is stop and wait ARQ in error control ?

Stop-and-Wait is an extended form of flow control to include retransmission of data in case of Lost or Damaged frames.
There are four main features added in it.

1. Sending device keeps a copy of the last frame transmitted until it receives the ACK for that frame.
2. Both data and ACK frames are numbered 0 and 1 alternately.
3. A data 0 frame is acknowledged by a ACK 1 frame indicating that the receiver has received data 0 and is now expecting data 1 .For retransmission to work, 
4. features are added to the basic flow control mechanism.