Transmission Mode

Two forms of data movement exist: parallel data transmission and serial data transmission.

• Parallel Transmission: Parallel data transmission involves the concurrent flow of bits of data through separate communications lines. This pattern resembles the flow of automobile traffic on a multilane 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 interactions between a computer and its printing unit. The printer usually located close to the computer, because parallel cables need many wires and may not work stably in long distance.

• Serial Data Transmission: Most data transmitted over telephone lines use a serial pattern. That is, each individual bit of information travels along its own communications path; the bits flow in a continuous stream along the communications channel. This pattern is analogous to the flow of traffic down a one-lane residential street.
  Serial transmission is typically slower than parallel transmission, because data are sent sequentially in a bit-by-bit fashion.