Serial Transmission
In, serial transmission, data is transmitted at one bit at a time in a continuous stream along the communications channel. For each direction of data flow, only one wire is used.
This pattern is analogous to the flow of traffic down a one-lane residential street. Most data transmitted over telephone lines uses a serial pattern. Serial Transmission is typically slower than parallel transmission, because data are sent sequentially in a bit-by-bit fashion.
Parallel Transmission
In the case of parallel data transmission, several bits of data are transmitted concurrently through separate communication lines. This resembles the flow of traffic on a multi lane highway. Internal transfer of binary data in a computer uses a parallel mode. If the computer uses a 32-bit internal structure, all the 32 bits of data are transferred simultaneously on 32-lane connections. Parallel data transmission is commonly used for interactitons between computer and is printing unit.
