2.1 Data Transmission

Serial transmission uses a single wire to transfer data bits one at a time, suitable for long distances with low cost but slow speed. Parallel transmission uses multiple wires to transfer data bits simultaneously, faster but more expensive and limited to short distances (about 5 meters) and more prone to interference. For example, a computer's internal components and simple computers like integrated circuits may use parallel transmission.

Simplex transmission sends data in only one direction, like a television broadcast. Duplex transmission allows data to be sent in both directions simultaneously, like a telephone conversation. Half - duplex transmission allows data to be sent in both directions but only one direction at a time, like a walkie - talkie.

Checksum counts the number of bits transmitted and the receiver checks if the count matches. Parity check adds a parity bit to a byte (usually 8 bits with the last bit as the parity bit) to ensure the data is sent accurately. It can be odd or even parity. For example, for 1001100 with even parity, the parity bit is 1 (because 1 + 0 + 0 + 1 + 1 + 0 + 0 = 3, an odd number, so add 1 to make it even). Check digit is used for identification numbers like barcodes to detect human error. Automatic Repeat reQuest (ARQ) makes the receiving device request the sender to resend a packet if an error is detected.