Reading & Processing Data and Text Input

Basic model, concept and technique to read symbols (might be characters, numbers, signals, any kind of pattern/symbol) from an input source, which might be a database, a file on the disk, a data packet incoming from the network, a measure by a sensor, or a key typed by the user. Focus is on how to organize loop iterations and handling, processing, reaction to the sequence of input data arriving within or requested by your own software application code.