Difference between synchronous and asynchronous communication?

Asynchronous:
-asynch comm there is no need to establish a connection before data transmission.
-asynch comm is used in packet swithed networks
-widely used for PC communication and is commonly used for e-mail applications, Internet access, and asynchronous PC-to-PC communications.
-data is transmitted one byte at a time with each byte containing one start bit, eight data bits, and one stop bit, thus yielding a total of ten bits.
- Disadvantage: overhead because every byte sent contains two extra bits (the start and stop bits) and therefore a substantial loss of performance.

Synchronous:
-first connection will be established and the communication
will take place.
-synch comm is used in circut swithed netwoks.
-data is transmitted as frames of large data blocks rather than bulky individual bytes. One advantage of synchronous is that control information is easily inserted at the beginning and end of each block to ensure constant timing, or synchronization.
-Another advantage of synchronous is that it is more efficient than asynchronous. For example, a 56 Kbps dial-up synchronous line can carry 7000 bytes per second (56000/8) compared to a 56 Kbps dial-up asynchronous line which can only carry 5600 bytes per second (56000/10).When transmitting large amounts of information, this translates into a significant increase in speed and performance.