acknowledgement (control character) (ACK)

In communication technology, the acknowledgment( ACK) is a feedback control code, an acknowledgement or the positive confirmation of receipt. The ACK signal is a transmission control character that is transmitted from a receiving data station, the data sink, to the sending data station, the data source, and confirms that a data packet has been received correctly and that the receiving side is again ready to receive.

To avoid unnecessary delays, for example if the data packet or the confirmation signal is lost, a time-out is used to set a time limit after which the data source retransmits the data packet to the data sink.

Positive (ACK) and negative (NAK) acknowledgements

The ACK character is part of the communication protocols and is responsible for the acknowledgement of receipt in the Automatic Repeat Request( ARQ). The Centronics interface is a handshaking line used by the printer to acknowledge receipt of data. Other printers use this line to transmit data from the printer to the host.

In the ASCII character set, the positive acknowledgement (ACK) has the ASCII value 006, the negative acknowledgement( NAK) has the value 021.