Conventions for Writing Big Oh Expressions

Certain conventions have evolved which concern how big oh expressions are normally written:

• First, it is common practice when writing big oh expressions to drop all but the most significant terms. Thus, instead of we simply write .
• Second, it is common practice to drop constant coefficients. Thus, instead of , we simply write . As a special case of this rule, if the function is a constant, instead of, say O(1024), we simply write O(1).

Of course, in order for a particular big oh expression to be the most useful, we prefer to find a tight asymptotic bound (see Definition ). For example, while it is not wrong to write , we prefer to write f(n)=O(n), which is a tight bound.

Certain big oh expressions occur so frequently that they are given names. Table  lists some of the commonly occurring big oh expressions and the usual name given to each of them.

Copyright © 1997 by Bruno R. Preiss, P.Eng. All rights reserved.