A chain smoker is, properly, a person who lights each new cigarette from the one he is just finishing. The term is most often used more loosely, referring to people who smoke more-or-less constantly, though not actually "chaining"; true chain smokers are relatively rare.
Chain smoking is the practice of lighting multiple new cigarettes from one that is finished.
Many smokers will, therefore, smoke several cigarettes in a row when they are able to in an attempt to stave off the physical discomfort associated with nicotine withdrawal.
In addition, many smokers will light up one cigarette after another as a way to combat stress or boredom, or because they are in a social situation where smoking is accepted, or even expected.
Chain rattling is the process of repeatedly running through the linked data areas searching for one which is of interest to the executing program.
The coil chains used in hoists and for locking or fastening purposes are of the open-link type, comprising solid interlocked rings, or of the stud-link type, in which a stud, or bar, across the link keeps the chain from kinking.
The chain is set in motion through the use of a discriminant stimulus, or prompt.