2. Letters, through the letter posted by the postman and the credit language, convey information to specific objects, exchange thoughts and feelings, and write letters to relatives and friends in person, which can not only convey thoughts and feelings, but also give the recipient a sense of intimacy.
3. Telegraph is an instant long-distance communication method, which is sent in the form of electric signal through special exchange line. Signals are coded, not words and numbers, and the commonly used code is Morse code.
4. The telephone transmits voice in two directions through electrical signals, and is set at the user end at the beginning and end of telephone communication, which can conveniently realize the conversation and dialogue between end users.
5, computer, database-based management system, computer technology to help managers improve decision-making level and improve business strategy. Information processing includes a series of work such as data collection, storage, processing, classification, collation, retrieval and release. ?