In ancient philosophy, an atom was the ultimate unit of matter on which more complex views of material reality were based. In computer programming, atomic describes a unitary action or object that is essentially indivisible, unchangeable, whole, and irreducible. Here are some usages:
1) In Structured Query Language , an atomic function is one that will either complete or return to its original state if a power interruption or an abnormal end occurs.
2) In some Unix -base operating systems, an atomic operation is one in which no change can take place in the time between the setting of a mask and the receiving of a signal to change the mask.
3) In some programming languages, including Lisp , an atom is the basic unit of executable code or data.